diff --git a/CHANGELOG.md b/CHANGELOG.md
index c054a0869..387a4c073 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -16,6 +16,14 @@ The release run heads these entries with the version and opens a fresh
 
 ## Unreleased
 
+- A file can be read in the dark: `HtmlConfig::color_scheme` is `light`, `dark`
+  or `system`, following the reader's `prefers-color-scheme`. Every view honors
+  it but the pdf one, and the colors the file authored give way to it. Bound in
+  the python, wasm, jni and apple bindings as `HtmlColorScheme`.
+- `FileTypeCapabilities::color_scheme` says whether a type's view honors it —
+  every type that renders but pdf, audio and video. Bound in the bindings too.
+- A text document reflowed to the viewport is inset 3mm from the screen edge
+  rather than starting at the first pixel of it.
 - Prose is no longer read as a csv. A separator that every field follows with a
   space, in fields long enough to be sentences, is punctuation; `a, b, c` with
   short values is still a csv. One record is a line, not a table.
diff --git a/apple/include/OdrCoreObjC/ODRFile.h b/apple/include/OdrCoreObjC/ODRFile.h
index 337ded16f..d1b070786 100644
--- a/apple/include/OdrCoreObjC/ODRFile.h
+++ b/apple/include/OdrCoreObjC/ODRFile.h
@@ -129,6 +129,8 @@ NS_SWIFT_NAME(FileTypeCapabilities)
 @property(nonatomic, readonly) BOOL decrypt;
 /// `ODRHtml` produces output for it.
 @property(nonatomic, readonly) BOOL translateHtml;
+/// The view it renders as honors `ODRHtmlConfig.colorScheme`.
+@property(nonatomic, readonly) BOOL colorScheme;
 @property(nonatomic, readonly) BOOL edit;
 @property(nonatomic, readonly) BOOL save;
 /// Saving with a password is supported.
diff --git a/apple/include/OdrCoreObjC/ODRHtml.h b/apple/include/OdrCoreObjC/ODRHtml.h
index c93b22a3c..8b46496c1 100644
--- a/apple/include/OdrCoreObjC/ODRHtml.h
+++ b/apple/include/OdrCoreObjC/ODRHtml.h
@@ -26,6 +26,17 @@ typedef NS_ENUM(NSInteger, ODRHtmlTableGridlines) {
   ODRHtmlTableGridlinesHard,
 } NS_SWIFT_NAME(HtmlTableGridlines);
 
+/// The colors the emitted HTML renders against. `ODRFileTypeCapabilities`
+/// says which views honor it.
+typedef NS_ENUM(NSInteger, ODRHtmlColorScheme) {
+  /// A white page, carrying the colors the document gives its content.
+  ODRHtmlColorSchemeLight = 0,
+  /// A dark page, which the document's own text and fill colors give way to.
+  ODRHtmlColorSchemeDark,
+  /// Light or dark, by the reader's `prefers-color-scheme`.
+  ODRHtmlColorSchemeSystem,
+} NS_SWIFT_NAME(HtmlColorScheme);
+
 /// Initial zoom of the emitted HTML on mobile (the viewport meta tag). Desktop
 /// browsers ignore it entirely.
 typedef NS_ENUM(NSInteger, ODRHtmlViewportMode) {
@@ -71,6 +82,8 @@ NS_SWIFT_NAME(HtmlConfig)
 @property(nonatomic) BOOL editable;
 @property(nonatomic) BOOL textDocumentMargin;
 
+@property(nonatomic) ODRHtmlColorScheme colorScheme;
+
 /// `nil` for no limit.
 @property(nonatomic, strong, nullable) NSValue *spreadsheetLimit;
 @property(nonatomic) BOOL spreadsheetLimitByContent;
diff --git a/apple/src/ODRFile.mm b/apple/src/ODRFile.mm
index d1dad972d..472f05f83 100644
--- a/apple/src/ODRFile.mm
+++ b/apple/src/ODRFile.mm
@@ -156,6 +156,7 @@ + (instancetype)capabilitiesWithHandle:
   result->_open = handle.open ? YES : NO;
   result->_decrypt = handle.decrypt ? YES : NO;
   result->_translateHtml = handle.translate_html ? YES : NO;
+  result->_colorScheme = handle.color_scheme ? YES : NO;
   result->_edit = handle.edit ? YES : NO;
   result->_save = handle.save ? YES : NO;
   result->_encrypt = handle.encrypt ? YES : NO;
diff --git a/apple/src/ODRHtml.mm b/apple/src/ODRHtml.mm
index 6881fb8dd..bb8fb3201 100644
--- a/apple/src/ODRHtml.mm
+++ b/apple/src/ODRHtml.mm
@@ -27,6 +27,10 @@
 ODR_SAME_ENUM(ODRHtmlTableGridlinesSoft, odr::HtmlTableGridlines::soft);
 ODR_SAME_ENUM(ODRHtmlTableGridlinesHard, odr::HtmlTableGridlines::hard);
 
+ODR_SAME_ENUM(ODRHtmlColorSchemeLight, odr::HtmlColorScheme::light);
+ODR_SAME_ENUM(ODRHtmlColorSchemeDark, odr::HtmlColorScheme::dark);
+ODR_SAME_ENUM(ODRHtmlColorSchemeSystem, odr::HtmlColorScheme::system);
+
 ODR_SAME_ENUM(ODRHtmlViewportModeAutomatic, odr::HtmlViewportMode::automatic);
 ODR_SAME_ENUM(ODRHtmlViewportModeFitWidth, odr::HtmlViewportMode::fit_width);
 ODR_SAME_ENUM(ODRHtmlViewportModeActualSize,
@@ -84,6 +88,7 @@ - (instancetype)initWithNativeConfig:(const odr::HtmlConfig &)config {
   _relativeResourcePaths = config.relative_resource_paths ? YES : NO;
   _editable = config.editable ? YES : NO;
   _textDocumentMargin = config.text_document_margin ? YES : NO;
+  _colorScheme = static_cast<ODRHtmlColorScheme>(config.color_scheme);
   if (config.spreadsheet_limit.has_value()) {
     const ODRTableDimensions limit = ODRTableDimensionsMake(
         config.spreadsheet_limit->rows, config.spreadsheet_limit->columns);
@@ -141,6 +146,7 @@ - (instancetype)initWithNativeConfig:(const odr::HtmlConfig &)config {
   config.relative_resource_paths = _relativeResourcePaths == YES;
   config.editable = _editable == YES;
   config.text_document_margin = _textDocumentMargin == YES;
+  config.color_scheme = static_cast<odr::HtmlColorScheme>(_colorScheme);
   if (_spreadsheetLimit != nil) {
     ODRTableDimensions limit{};
     [_spreadsheetLimit getValue:&limit size:sizeof(limit)];
diff --git a/jni/CMakeLists.txt b/jni/CMakeLists.txt
index e0f36089a..e5ced466a 100644
--- a/jni/CMakeLists.txt
+++ b/jni/CMakeLists.txt
@@ -105,6 +105,7 @@ add_jar(odr_java
         "java/app/opendocument/core/GuardedNativeResource.java"
         "java/app/opendocument/core/HorizontalAlign.java"
         "java/app/opendocument/core/Html.java"
+        "java/app/opendocument/core/HtmlColorScheme.java"
         "java/app/opendocument/core/HtmlConfig.java"
         "java/app/opendocument/core/HtmlPage.java"
         "java/app/opendocument/core/HtmlResource.java"
diff --git a/jni/java/app/opendocument/core/FileTypeCapabilities.java b/jni/java/app/opendocument/core/FileTypeCapabilities.java
index 8bb1369c2..2a36b7743 100644
--- a/jni/java/app/opendocument/core/FileTypeCapabilities.java
+++ b/jni/java/app/opendocument/core/FileTypeCapabilities.java
@@ -22,6 +22,9 @@ public final class FileTypeCapabilities {
   /** {@link Html#translate} produces output. */
   public final boolean translateHtml;
 
+  /** The view this type renders as honors {@link HtmlConfig#colorScheme}. */
+  public final boolean colorScheme;
+
   /** {@link Document#isEditable} can be {@code true}. */
   public final boolean edit;
 
@@ -36,6 +39,7 @@ public final class FileTypeCapabilities {
       boolean open,
       boolean decrypt,
       boolean translateHtml,
+      boolean colorScheme,
       boolean edit,
       boolean save,
       boolean encrypt) {
@@ -43,6 +47,7 @@ public final class FileTypeCapabilities {
     this.open = open;
     this.decrypt = decrypt;
     this.translateHtml = translateHtml;
+    this.colorScheme = colorScheme;
     this.edit = edit;
     this.save = save;
     this.encrypt = encrypt;
diff --git a/jni/java/app/opendocument/core/HtmlColorScheme.java b/jni/java/app/opendocument/core/HtmlColorScheme.java
new file mode 100644
index 000000000..bdd96409c
--- /dev/null
+++ b/jni/java/app/opendocument/core/HtmlColorScheme.java
@@ -0,0 +1,14 @@
+package app.opendocument.core;
+
+/** Mirrors {@code odr::HtmlColorScheme}; constant order must match the C++ declaration. */
+public enum HtmlColorScheme {
+  LIGHT, DARK, SYSTEM;
+
+  static HtmlColorScheme fromNative(int code) {
+    return code < 0 ? null : values()[code];
+  }
+
+  int toNative() {
+    return ordinal();
+  }
+}
diff --git a/jni/java/app/opendocument/core/HtmlConfig.java b/jni/java/app/opendocument/core/HtmlConfig.java
index 7621ef191..4d9c3a61c 100644
--- a/jni/java/app/opendocument/core/HtmlConfig.java
+++ b/jni/java/app/opendocument/core/HtmlConfig.java
@@ -23,6 +23,9 @@ public final class HtmlConfig {
 
   public boolean textDocumentMargin = false;
 
+  /** The colors a document renders against. */
+  public HtmlColorScheme colorScheme = HtmlColorScheme.LIGHT;
+
   /** {@code null} disables the spreadsheet limit. */
   public TableDimensions spreadsheetLimit = new TableDimensions(10000, 500);
   public boolean spreadsheetLimitByContent = true;
diff --git a/jni/src/jni_style.cpp b/jni/src/jni_style.cpp
index 84a6c6c89..cddad91c3 100644
--- a/jni/src/jni_style.cpp
+++ b/jni/src/jni_style.cpp
@@ -296,11 +296,12 @@ jobject
 make_file_type_capabilities(JNIEnv *env,
                             const odr::FileTypeCapabilities &capabilities) {
   return new_object(env, "app/opendocument/core/FileTypeCapabilities",
-                    "(ZZZZZZZ)V",
+                    "(ZZZZZZZZ)V",
                     static_cast<jboolean>(capabilities.detect_by_content),
                     static_cast<jboolean>(capabilities.open),
                     static_cast<jboolean>(capabilities.decrypt),
                     static_cast<jboolean>(capabilities.translate_html),
+                    static_cast<jboolean>(capabilities.color_scheme),
                     static_cast<jboolean>(capabilities.edit),
                     static_cast<jboolean>(capabilities.save),
                     static_cast<jboolean>(capabilities.encrypt));
@@ -344,6 +345,9 @@ jobject html_config_to_java(JNIEnv *env, const odr::HtmlConfig &config) {
   set_boolean("relativeResourcePaths", config.relative_resource_paths);
   set_boolean("editable", config.editable);
   set_boolean("textDocumentMargin", config.text_document_margin);
+  set_object("colorScheme", "Lapp/opendocument/core/HtmlColorScheme;",
+             enum_from_code(env, "app/opendocument/core/HtmlColorScheme",
+                            static_cast<jint>(config.color_scheme)));
   set_object("spreadsheetLimit", "Lapp/opendocument/core/TableDimensions;",
              config.spreadsheet_limit.has_value()
                  ? make_table_dimensions(env, *config.spreadsheet_limit)
@@ -452,6 +456,14 @@ odr::HtmlConfig html_config_from_java(JNIEnv *env, jobject config) {
   result.relative_resource_paths = get_boolean("relativeResourcePaths");
   result.editable = get_boolean("editable");
   result.text_document_margin = get_boolean("textDocumentMargin");
+  {
+    const jint code = enum_ordinal(
+        env,
+        get_object("colorScheme", "Lapp/opendocument/core/HtmlColorScheme;"));
+    if (code >= 0) {
+      result.color_scheme = static_cast<odr::HtmlColorScheme>(code);
+    }
+  }
   {
     jobject limit = get_object("spreadsheetLimit",
                                "Lapp/opendocument/core/TableDimensions;");
diff --git a/jni/tests/app/opendocument/core/HtmlTest.java b/jni/tests/app/opendocument/core/HtmlTest.java
index b5b9bc86c..747f79f8c 100644
--- a/jni/tests/app/opendocument/core/HtmlTest.java
+++ b/jni/tests/app/opendocument/core/HtmlTest.java
@@ -80,6 +80,22 @@ void viewportModeReachesTheHtml() throws IOException {
     assertTrue(renderOdt(raw).contains("<meta name=\"viewport\" content=\"width=420\"/>"));
   }
 
+  /** The C++ suite covers what the scheme paints; this only proves it crosses JNI. */
+  @Test
+  void colorSchemeReachesTheHtml() throws IOException {
+    assertEquals(HtmlColorScheme.LIGHT, new HtmlConfig().colorScheme);
+    assertTrue(!renderOdt(new HtmlConfig()).contains("prefers-color-scheme"));
+
+    HtmlConfig system = new HtmlConfig();
+    system.colorScheme = HtmlColorScheme.SYSTEM;
+    assertTrue(renderOdt(system).contains("media=\"(prefers-color-scheme: dark)\""));
+
+    Path cache = Files.createDirectories(tempDir.resolve("scheme"));
+    DecodedFile file = Odr.open(TestFiles.odtFile(tempDir).toString());
+    HtmlConfig readBack = Html.translate(file, cache.toString(), system).config();
+    assertEquals(HtmlColorScheme.SYSTEM, readBack.colorScheme);
+  }
+
   @Test
   void translateText() throws IOException {
     Html html = translateOffline(TestFiles.txtFile(tempDir));
diff --git a/jni/tests/app/opendocument/core/MetaTest.java b/jni/tests/app/opendocument/core/MetaTest.java
index 1697b25e6..a54187c79 100644
--- a/jni/tests/app/opendocument/core/MetaTest.java
+++ b/jni/tests/app/opendocument/core/MetaTest.java
@@ -72,6 +72,7 @@ void capabilitiesByFileType() {
     FileTypeCapabilities odt = Odr.capabilitiesByFileType(FileType.OPENDOCUMENT_TEXT);
     assertTrue(odt.open);
     assertTrue(odt.translateHtml);
+    assertTrue(odt.colorScheme);
     assertTrue(odt.edit);
 
     // detected and named, but there is no decoder behind it
@@ -82,6 +83,11 @@ void capabilitiesByFileType() {
 
     // spreadsheet editing is force-disabled
     assertFalse(Odr.capabilitiesByFileType(FileType.OPENDOCUMENT_SPREADSHEET).edit);
+
+    // a pdf renders, but paints its own page backgrounds
+    FileTypeCapabilities pdf = Odr.capabilitiesByFileType(FileType.PORTABLE_DOCUMENT_FORMAT);
+    assertTrue(pdf.translateHtml);
+    assertFalse(pdf.colorScheme);
   }
 
   @Test
diff --git a/python/src/bind_file.cpp b/python/src/bind_file.cpp
index b0eaf79d6..ac48ef545 100644
--- a/python/src/bind_file.cpp
+++ b/python/src/bind_file.cpp
@@ -145,6 +145,7 @@ void odr_python::bind_file(py::module_ &m) {
       .def_readwrite("decrypt", &odr::FileTypeCapabilities::decrypt)
       .def_readwrite("translate_html",
                      &odr::FileTypeCapabilities::translate_html)
+      .def_readwrite("color_scheme", &odr::FileTypeCapabilities::color_scheme)
       .def_readwrite("edit", &odr::FileTypeCapabilities::edit)
       .def_readwrite("save", &odr::FileTypeCapabilities::save)
       .def_readwrite("encrypt", &odr::FileTypeCapabilities::encrypt);
diff --git a/python/src/bind_html.cpp b/python/src/bind_html.cpp
index 375b838ce..956b1d177 100644
--- a/python/src/bind_html.cpp
+++ b/python/src/bind_html.cpp
@@ -30,6 +30,11 @@ void odr_python::bind_html(py::module_ &m) {
       .value("soft", odr::HtmlTableGridlines::soft)
       .value("hard", odr::HtmlTableGridlines::hard);
 
+  py::enum_<odr::HtmlColorScheme>(m, "HtmlColorScheme")
+      .value("light", odr::HtmlColorScheme::light)
+      .value("dark", odr::HtmlColorScheme::dark)
+      .value("system", odr::HtmlColorScheme::system);
+
   py::enum_<odr::HtmlViewportMode>(m, "HtmlViewportMode")
       .value("automatic", odr::HtmlViewportMode::automatic)
       .value("fit_width", odr::HtmlViewportMode::fit_width)
@@ -75,6 +80,7 @@ void odr_python::bind_html(py::module_ &m) {
       .def_readwrite("editable", &odr::HtmlConfig::editable)
       .def_readwrite("text_document_margin",
                      &odr::HtmlConfig::text_document_margin)
+      .def_readwrite("color_scheme", &odr::HtmlConfig::color_scheme)
       .def_readwrite("spreadsheet_limit", &odr::HtmlConfig::spreadsheet_limit)
       .def_readwrite("spreadsheet_limit_by_content",
                      &odr::HtmlConfig::spreadsheet_limit_by_content)
diff --git a/python/tests/test_html.py b/python/tests/test_html.py
index be5382c01..e55c14346 100644
--- a/python/tests/test_html.py
+++ b/python/tests/test_html.py
@@ -26,6 +26,14 @@ def test_html_config_defaults():
     assert config.spreadsheet_limit.rows == 100
 
 
+def test_html_config_color_scheme_defaults():
+    config = pyodr.HtmlConfig()
+    assert config.color_scheme == pyodr.HtmlColorScheme.light
+
+    config.color_scheme = pyodr.HtmlColorScheme.system
+    assert config.color_scheme == pyodr.HtmlColorScheme.system
+
+
 def test_html_config_viewport_defaults():
     config = pyodr.HtmlConfig()
     assert config.viewport_mode == pyodr.HtmlViewportMode.automatic
diff --git a/python/tests/test_meta.py b/python/tests/test_meta.py
index 01cde621f..8c0a71acf 100644
--- a/python/tests/test_meta.py
+++ b/python/tests/test_meta.py
@@ -96,6 +96,7 @@ def test_capabilities_by_file_type():
     odt = pyodr.capabilities_by_file_type(pyodr.FileType.opendocument_text)
     assert odt.open
     assert odt.translate_html
+    assert odt.color_scheme
     assert odt.edit
 
     # detected and named, but there is no decoder behind it
@@ -109,6 +110,11 @@ def test_capabilities_by_file_type():
         pyodr.FileType.opendocument_spreadsheet
     ).edit
 
+    # a pdf renders, but paints its own page backgrounds
+    pdf = pyodr.capabilities_by_file_type(pyodr.FileType.portable_document_format)
+    assert pdf.translate_html
+    assert not pdf.color_scheme
+
 
 def test_decoded_file_capabilities(odt_path):
     capabilities = pyodr.open(str(odt_path)).capabilities()
diff --git a/src/odr/file.cpp b/src/odr/file.cpp
index e64fc15e1..c91d2e488 100644
--- a/src/odr/file.cpp
+++ b/src/odr/file.cpp
@@ -172,6 +172,8 @@ FileTypeCapabilities DecodedFile::capabilities() const {
   // an encrypted file has to be decrypted before it renders
   result.translate_html =
       result.translate_html && encryption_state() != EncryptionState::encrypted;
+  // there is no scheme without html
+  result.color_scheme = result.color_scheme && result.translate_html;
 
   // `edit`/`save`/`encrypt` stay as declared — resolving them would mean
   // decoding the document; ask `Document` for the precise answer
diff --git a/src/odr/file.hpp b/src/odr/file.hpp
index 61ed44c74..45aea9375 100644
--- a/src/odr/file.hpp
+++ b/src/odr/file.hpp
@@ -182,6 +182,7 @@ struct FileTypeCapabilities final {
   bool open{};              ///< a decoder exists; @ref odr::open can decode it
   bool decrypt{};           ///< encrypted instances can be decrypted
   bool translate_html{};    ///< @ref html::translate produces output
+  bool color_scheme{};      ///< the view honors @ref HtmlConfig::color_scheme
   bool edit{};              ///< @ref Document::is_editable can be `true`
   bool save{};              ///< @ref Document::save is supported
   bool encrypt{}; ///< @ref Document::save with a password is supported
diff --git a/src/odr/html.hpp b/src/odr/html.hpp
index 4a4b06cf8..2f7cfa8ee 100644
--- a/src/odr/html.hpp
+++ b/src/odr/html.hpp
@@ -73,6 +73,14 @@ enum class HtmlTableGridlines {
   hard,
 };
 
+/// @brief The colors the emitted HTML renders against. @ref
+/// FileTypeCapabilities::color_scheme says which views honor it.
+enum class HtmlColorScheme {
+  light,  ///< a white page, carrying the colors the document gives its content
+  dark,   ///< a dark page, which the document's own colors give way to
+  system, ///< `light` or `dark`, by the reader's `prefers-color-scheme`
+};
+
 /// @brief Initial zoom of the emitted HTML on mobile (viewport meta tag).
 /// Desktop browsers ignore the tag entirely.
 enum class HtmlViewportMode {
@@ -124,6 +132,9 @@ struct HtmlConfig {
   // text document margin
   bool text_document_margin{false};
 
+  // colors the output renders against
+  HtmlColorScheme color_scheme{HtmlColorScheme::light};
+
   // spreadsheet table limit
   std::optional<TableDimensions> spreadsheet_limit{TableDimensions(10000, 500)};
   bool spreadsheet_limit_by_content{true};
diff --git a/src/odr/internal/file_type_table.cpp b/src/odr/internal/file_type_table.cpp
index 093ecd948..61c6ecdd1 100644
--- a/src/odr/internal/file_type_table.cpp
+++ b/src/odr/internal/file_type_table.cpp
@@ -269,6 +269,7 @@ constexpr std::array table{
          .open = true,
          .decrypt = true,
          .translate_html = true,
+         .color_scheme = true,
          .edit = true,
          .save = true}},
     Row{FileType::opendocument_presentation,
@@ -281,6 +282,7 @@ constexpr std::array table{
          .open = true,
          .decrypt = true,
          .translate_html = true,
+         .color_scheme = true,
          .edit = true,
          .save = true}},
     // ODF spreadsheet editing is force-disabled, see `odf::Document`.
@@ -294,6 +296,7 @@ constexpr std::array table{
          .open = true,
          .decrypt = true,
          .translate_html = true,
+         .color_scheme = true,
          .save = true}},
     Row{FileType::opendocument_graphics,
         "odg"sv,
@@ -305,6 +308,7 @@ constexpr std::array table{
          .open = true,
          .decrypt = true,
          .translate_html = true,
+         .color_scheme = true,
          .edit = true,
          .save = true}},
 
@@ -318,6 +322,7 @@ constexpr std::array table{
          .open = true,
          .decrypt = true,
          .translate_html = true,
+         .color_scheme = true,
          .edit = true,
          .save = true}},
     Row{FileType::office_open_xml_presentation,
@@ -329,7 +334,8 @@ constexpr std::array table{
         {.detect_by_content = true,
          .open = true,
          .decrypt = true,
-         .translate_html = true}},
+         .translate_html = true,
+         .color_scheme = true}},
     Row{FileType::office_open_xml_workbook,
         "xlsx"sv,
         xlsx_extensions,
@@ -339,7 +345,8 @@ constexpr std::array table{
         {.detect_by_content = true,
          .open = true,
          .decrypt = true,
-         .translate_html = true}},
+         .translate_html = true,
+         .color_scheme = true}},
     Row{FileType::office_open_xml_encrypted,
         "ooxml_encrypted"sv,
         {},
@@ -362,21 +369,30 @@ constexpr std::array table{
         doc_mimetypes,
         FileCategory::document,
         DocumentType::text,
-        {.detect_by_content = true, .open = true, .translate_html = true}},
+        {.detect_by_content = true,
+         .open = true,
+         .translate_html = true,
+         .color_scheme = true}},
     Row{FileType::legacy_powerpoint_presentation,
         "ppt"sv,
         ppt_extensions,
         ppt_mimetypes,
         FileCategory::document,
         DocumentType::presentation,
-        {.detect_by_content = true, .open = true, .translate_html = true}},
+        {.detect_by_content = true,
+         .open = true,
+         .translate_html = true,
+         .color_scheme = true}},
     Row{FileType::legacy_excel_worksheets,
         "xls"sv,
         xls_extensions,
         xls_mimetypes,
         FileCategory::document,
         DocumentType::spreadsheet,
-        {.detect_by_content = true, .open = true, .translate_html = true}},
+        {.detect_by_content = true,
+         .open = true,
+         .translate_html = true,
+         .color_scheme = true}},
 
     // Recognised by magic so a caller can name the type, but there is no
     // decoder behind either of these.
@@ -412,21 +428,30 @@ constexpr std::array table{
         txt_mimetypes,
         FileCategory::text,
         DocumentType::unknown,
-        {.detect_by_content = true, .open = true, .translate_html = true}},
+        {.detect_by_content = true,
+         .open = true,
+         .translate_html = true,
+         .color_scheme = true}},
     Row{FileType::comma_separated_values,
         "csv"sv,
         csv_extensions,
         csv_mimetypes,
         FileCategory::text,
         DocumentType::spreadsheet,
-        {.detect_by_content = true, .open = true, .translate_html = true}},
+        {.detect_by_content = true,
+         .open = true,
+         .translate_html = true,
+         .color_scheme = true}},
     Row{FileType::javascript_object_notation,
         "json"sv,
         json_extensions,
         json_mimetypes,
         FileCategory::text,
         DocumentType::unknown,
-        {.detect_by_content = true, .open = true, .translate_html = true}},
+        {.detect_by_content = true,
+         .open = true,
+         .translate_html = true,
+         .color_scheme = true}},
     // Classified for callers that route files by type; there is no decoder.
     Row{FileType::markdown,
         "md"sv,
@@ -442,14 +467,20 @@ constexpr std::array table{
         zip_mimetypes,
         FileCategory::archive,
         DocumentType::unknown,
-        {.detect_by_content = true, .open = true, .translate_html = true}},
+        {.detect_by_content = true,
+         .open = true,
+         .translate_html = true,
+         .color_scheme = true}},
     Row{FileType::compound_file_binary_format,
         "cfb"sv,
         cfb_extensions,
         cfb_mimetypes,
         FileCategory::archive,
         DocumentType::unknown,
-        {.detect_by_content = true, .open = true, .translate_html = true}},
+        {.detect_by_content = true,
+         .open = true,
+         .translate_html = true,
+         .color_scheme = true}},
 
     Row{FileType::portable_network_graphics,
         "png"sv,
@@ -457,35 +488,50 @@ constexpr std::array table{
         png_mimetypes,
         FileCategory::image,
         DocumentType::unknown,
-        {.detect_by_content = true, .open = true, .translate_html = true}},
+        {.detect_by_content = true,
+         .open = true,
+         .translate_html = true,
+         .color_scheme = true}},
     Row{FileType::graphics_interchange_format,
         "gif"sv,
         gif_extensions,
         gif_mimetypes,
         FileCategory::image,
         DocumentType::unknown,
-        {.detect_by_content = true, .open = true, .translate_html = true}},
+        {.detect_by_content = true,
+         .open = true,
+         .translate_html = true,
+         .color_scheme = true}},
     Row{FileType::jpeg,
         "jpg"sv,
         jpg_extensions,
         jpg_mimetypes,
         FileCategory::image,
         DocumentType::unknown,
-        {.detect_by_content = true, .open = true, .translate_html = true}},
+        {.detect_by_content = true,
+         .open = true,
+         .translate_html = true,
+         .color_scheme = true}},
     Row{FileType::bitmap_image_file,
         "bmp"sv,
         bmp_extensions,
         bmp_mimetypes,
         FileCategory::image,
         DocumentType::unknown,
-        {.detect_by_content = true, .open = true, .translate_html = true}},
+        {.detect_by_content = true,
+         .open = true,
+         .translate_html = true,
+         .color_scheme = true}},
     Row{FileType::starview_metafile,
         "svm"sv,
         svm_extensions,
         svm_mimetypes,
         FileCategory::image,
         DocumentType::unknown,
-        {.detect_by_content = true, .open = true, .translate_html = true}},
+        {.detect_by_content = true,
+         .open = true,
+         .translate_html = true,
+         .color_scheme = true}},
 
     Row{FileType::truetype_font,
         "ttf"sv,
@@ -493,14 +539,20 @@ constexpr std::array table{
         ttf_mimetypes,
         FileCategory::font,
         DocumentType::unknown,
-        {.detect_by_content = true, .open = true, .translate_html = true}},
+        {.detect_by_content = true,
+         .open = true,
+         .translate_html = true,
+         .color_scheme = true}},
     Row{FileType::opentype_font,
         "otf"sv,
         otf_extensions,
         otf_mimetypes,
         FileCategory::font,
         DocumentType::unknown,
-        {.detect_by_content = true, .open = true, .translate_html = true}},
+        {.detect_by_content = true,
+         .open = true,
+         .translate_html = true,
+         .color_scheme = true}},
 
     // Named but not decoded: `open` wraps the bytes and `translate_html` hands
     // them to the browser in an `<img>` or a player. Nothing reads a pixel or
@@ -511,28 +563,40 @@ constexpr std::array table{
         webp_mimetypes,
         FileCategory::image,
         DocumentType::unknown,
-        {.detect_by_content = true, .open = true, .translate_html = true}},
+        {.detect_by_content = true,
+         .open = true,
+         .translate_html = true,
+         .color_scheme = true}},
     Row{FileType::tagged_image_file_format,
         "tiff"sv,
         tiff_extensions,
         tiff_mimetypes,
         FileCategory::image,
         DocumentType::unknown,
-        {.detect_by_content = true, .open = true, .translate_html = true}},
+        {.detect_by_content = true,
+         .open = true,
+         .translate_html = true,
+         .color_scheme = true}},
     Row{FileType::high_efficiency_image_format,
         "heif"sv,
         heif_extensions,
         heif_mimetypes,
         FileCategory::image,
         DocumentType::unknown,
-        {.detect_by_content = true, .open = true, .translate_html = true}},
+        {.detect_by_content = true,
+         .open = true,
+         .translate_html = true,
+         .color_scheme = true}},
     Row{FileType::av1_image_file_format,
         "avif"sv,
         avif_extensions,
         avif_mimetypes,
         FileCategory::image,
         DocumentType::unknown,
-        {.detect_by_content = true, .open = true, .translate_html = true}},
+        {.detect_by_content = true,
+         .open = true,
+         .translate_html = true,
+         .color_scheme = true}},
 
     Row{FileType::mpeg_audio,
         "mp3"sv,
@@ -615,49 +679,70 @@ constexpr std::array table{
         svg_mimetypes,
         FileCategory::image,
         DocumentType::unknown,
-        {.detect_by_content = true, .open = true, .translate_html = true}},
+        {.detect_by_content = true,
+         .open = true,
+         .translate_html = true,
+         .color_scheme = true}},
     Row{FileType::windows_icon,
         "ico"sv,
         ico_extensions,
         ico_mimetypes,
         FileCategory::image,
         DocumentType::unknown,
-        {.detect_by_content = true, .open = true, .translate_html = true}},
+        {.detect_by_content = true,
+         .open = true,
+         .translate_html = true,
+         .color_scheme = true}},
     Row{FileType::jpeg_xl,
         "jxl"sv,
         jxl_extensions,
         jxl_mimetypes,
         FileCategory::image,
         DocumentType::unknown,
-        {.detect_by_content = true, .open = true, .translate_html = true}},
+        {.detect_by_content = true,
+         .open = true,
+         .translate_html = true,
+         .color_scheme = true}},
     Row{FileType::jpeg_2000,
         "jp2"sv,
         jp2_extensions,
         jp2_mimetypes,
         FileCategory::image,
         DocumentType::unknown,
-        {.detect_by_content = true, .open = true, .translate_html = true}},
+        {.detect_by_content = true,
+         .open = true,
+         .translate_html = true,
+         .color_scheme = true}},
     Row{FileType::photoshop_document,
         "psd"sv,
         psd_extensions,
         psd_mimetypes,
         FileCategory::image,
         DocumentType::unknown,
-        {.detect_by_content = true, .open = true, .translate_html = true}},
+        {.detect_by_content = true,
+         .open = true,
+         .translate_html = true,
+         .color_scheme = true}},
     Row{FileType::windows_metafile,
         "wmf"sv,
         wmf_extensions,
         wmf_mimetypes,
         FileCategory::image,
         DocumentType::unknown,
-        {.detect_by_content = true, .open = true, .translate_html = true}},
+        {.detect_by_content = true,
+         .open = true,
+         .translate_html = true,
+         .color_scheme = true}},
     Row{FileType::enhanced_metafile,
         "emf"sv,
         emf_extensions,
         emf_mimetypes,
         FileCategory::image,
         DocumentType::unknown,
-        {.detect_by_content = true, .open = true, .translate_html = true}},
+        {.detect_by_content = true,
+         .open = true,
+         .translate_html = true,
+         .color_scheme = true}},
 
     // Not decoded: it renders as a source view of itself.
     Row{FileType::xml,
@@ -666,7 +751,10 @@ constexpr std::array table{
         xml_mimetypes,
         FileCategory::text,
         DocumentType::unknown,
-        {.detect_by_content = true, .open = true, .translate_html = true}},
+        {.detect_by_content = true,
+         .open = true,
+         .translate_html = true,
+         .color_scheme = true}},
 };
 
 /// Finds the row whose list, selected by @p list, contains @p needle.
diff --git a/src/odr/internal/html/document.cpp b/src/odr/internal/html/document.cpp
index 06d0d5d71..a73530af0 100644
--- a/src/odr/internal/html/document.cpp
+++ b/src/odr/internal/html/document.cpp
@@ -54,9 +54,12 @@ void front(const Document &document, const WritingState &state,
                           : std::nullopt);
 
   write_document_style(state);
+  write_document_dark_style(state);
   write_search_style(state);
+  write_search_dark_style(state);
   if (document.document_type() == DocumentType::spreadsheet) {
     write_spreadsheet_style(state);
+    write_spreadsheet_dark_style(state);
   }
 
   out.write_header_end();
@@ -317,7 +320,8 @@ class TextHtmlFragment final : public HtmlFragmentBase {
       out.write_element_end("div");
       out.write_element_end("div");
     } else {
-      out.write_element_begin("div");
+      out.write_element_begin("div",
+                              HtmlElementOptions().set_class("odr-text-flow"));
       translate_children(element.children(), state);
       out.write_element_end("div");
     }
diff --git a/src/odr/internal/html/filesystem.cpp b/src/odr/internal/html/filesystem.cpp
index 5cfe12370..ad8b14c85 100644
--- a/src/odr/internal/html/filesystem.cpp
+++ b/src/odr/internal/html/filesystem.cpp
@@ -189,7 +189,9 @@ class HtmlServiceImpl final : public HtmlService {
     out.write_header_title("odr");
     write_viewport_meta(out, config(), false);
     write_filesystem_style(state);
+    write_filesystem_dark_style(state);
     write_search_style(state);
+    write_search_dark_style(state);
     out.write_header_end();
 
     out.write_body_begin();
diff --git a/src/odr/internal/html/font_file.cpp b/src/odr/internal/html/font_file.cpp
index ffb6baa3f..b1555e455 100644
--- a/src/odr/internal/html/font_file.cpp
+++ b/src/odr/internal/html/font_file.cpp
@@ -9,6 +9,7 @@
 #include <odr/internal/font/sfnt_font.hpp>
 #include <odr/internal/font/sfnt_transform.hpp>
 #include <odr/internal/html/common.hpp>
+#include <odr/internal/html/frontend.hpp>
 #include <odr/internal/html/html_service.hpp>
 #include <odr/internal/html/html_writer.hpp>
 #include <odr/internal/util/stream_util.hpp>
@@ -122,6 +123,15 @@ class HtmlServiceImpl final : public HtmlService {
     out.out() << ".gid{font-size:.6em;color:#888;}";
     out.out() << "</style>";
 
+    if (writes_dark_style(config())) {
+      out.write_header_style_begin(dark_style_media(config()));
+      out.out() << ":root{color-scheme:dark}";
+      out.out() << "body{background:#0d1117;color:#e6edf3;}";
+      out.out() << ".cell{border-color:#30363d;}";
+      out.out() << ".gid{color:#8b949e;}";
+      out.write_header_style_end();
+    }
+
     out.out() << "<h1>" << escape_text(font->name()) << "</h1>";
     out.out() << "<p>glyphs: " << font->glyph_count()
               << " &middot; units/em: " << font->units_per_em()
diff --git a/src/odr/internal/html/frontend.cpp b/src/odr/internal/html/frontend.cpp
index 0f3063b02..733406993 100644
--- a/src/odr/internal/html/frontend.cpp
+++ b/src/odr/internal/html/frontend.cpp
@@ -35,12 +35,33 @@ x-s{display:inline}
    Not a negative `z-index`, which is one too but takes the page out of reach of
    hit testing. */
 .odr-page-outer{display:flex;margin:0 16px;background:#fff;box-shadow:0 1px 4px rgba(0,0,0,.5);isolation:isolate}
+/* Reflowed to the viewport there is no page box to inset the text. A physical
+   measure, like the page margin it stands in for. */
+.odr-text-flow{padding:3mm}
 /* The label is text rather than a `::marker`, which no selection would copy.
    It hangs into the item's padding so wrapped lines align under the text. */
 .odr-list-item{padding-left:2em}
 .odr-list-marker{display:inline-block;min-width:2em;margin-left:-2em;white-space:pre}
 )css";
 
+/// Dark counterpart of the style above. The `media` attribute of the element
+/// carrying it gates it — a rule inside a query cannot beat an inline color.
+constexpr std::string_view document_dark_css = R"css(
+:root{color-scheme:dark}
+body{background:#0d1117;color:#e6edf3}
+/* The step to the page is what makes it read as a sheet. */
+.odr-background{background:#010409}
+.odr-page-outer{background-color:#161b22!important;box-shadow:0 1px 4px rgba(0,0,0,.8)}
+/* Fills give way to the page, text to one legible against it.
+   `background-image` is left alone: a page printed on a picture keeps it. */
+div,table,tr,td,x-p,x-s{background-color:transparent!important}
+/* A shape's fill is an svg `fill` (`translate_drawing_style`), not a
+   background, and gives way like one. The stroke stays: it is the line. */
+svg,svg *{fill:transparent!important}
+td,x-p,x-s{color:#e6edf3!important}
+a,a x-p,a x-s{color:#6cb6ff!important}
+)css";
+
 /// No `text-overflow`: it sat on `td`, whose overflow is visible, and making it
 /// work would mean clipping.
 constexpr std::string_view spreadsheet_css = R"css(
@@ -88,6 +109,21 @@ body{margin:0;background:var(--odr-sheet-canvas)}
 .odr-sheet-sort-asc::after{content:"\25B4"}
 )css";
 
+constexpr std::string_view spreadsheet_dark_css = R"css(
+:root{
+--odr-sheet-line:#30363d;
+--odr-sheet-rule:#484f58;
+--odr-sheet-ruler:#161b22;
+--odr-sheet-ruler-text:#8b949e;
+--odr-sheet-canvas:#0d1117;
+--odr-sheet-wash:rgba(255,255,255,.05);
+--odr-sheet-wash-pinned:rgba(255,255,255,.10);
+--odr-sheet-wash-ruler:rgba(255,255,255,.12);
+--odr-sheet-focus:#4c8dff;
+}
+.odr-sheet{background-color:#161b22!important}
+)css";
+
 /// A whole-pixel line height, because the line numbers are a second column
 /// whose cells are sized to the lines by script - a fractional line would round
 /// per cell and the two columns would drift apart.
@@ -115,6 +151,19 @@ body{margin:0;background:#fff}
 [contenteditable]:focus{outline:none}
 )css";
 
+/// The gutter steps the other way in dark: lighter than the ground.
+constexpr std::string_view text_dark_css = R"css(
+:root{
+color-scheme:dark;
+--odr-text-fg:#e6edf3;
+--odr-text-muted:#8b949e;
+--odr-text-line:#30363d;
+--odr-text-gutter:#161b22;
+--odr-text-wash:rgba(255,255,255,.05);
+}
+body{background:#0d1117}
+)css";
+
 /// No numbered gutter - the numbers would be ours, not the file's. The column
 /// carries the fold handles, and every line reserves it.
 constexpr std::string_view xml_css = R"css(
@@ -150,6 +199,21 @@ body{margin:0;background:#fff}
 .odr-xml-decl,.odr-xml-doctype,.odr-xml-pi{color:var(--odr-xml-meta)}
 )css";
 
+constexpr std::string_view xml_dark_css = R"css(
+:root{
+color-scheme:dark;
+--odr-xml-text:#e6edf3;
+--odr-xml-muted:#8b949e;
+--odr-xml-punct:#9198a1;
+--odr-xml-name:#7ee787;
+--odr-xml-attr:#ffa657;
+--odr-xml-value:#a5d6ff;
+--odr-xml-meta:#d2a8ff;
+}
+body{background:#0d1117}
+.odr-xml summary:hover{background:rgba(255,255,255,.06)}
+)css";
+
 constexpr std::string_view filesystem_css = R"css(
 :root{
 --odr-files-line:#e3e5e8;
@@ -172,6 +236,19 @@ body{margin:0;background:#fff;color:#1f2328;font:13px/1.5 var(--odr-files-font)}
 .odr-files-action a:hover{background:rgba(0,0,0,.07);color:var(--odr-files-link)}
 )css";
 
+/// The washes lighten rather than darken: a black one paints nothing here.
+constexpr std::string_view filesystem_dark_css = R"css(
+:root{
+color-scheme:dark;
+--odr-files-line:#30363d;
+--odr-files-muted:#8b949e;
+--odr-files-link:#6cb6ff;
+}
+body{background:#0d1117;color:#e6edf3}
+.odr-files tbody tr:hover>*{background-image:linear-gradient(rgba(255,255,255,.05),rgba(255,255,255,.05))}
+.odr-files-action a:hover{background:rgba(255,255,255,.08)}
+)css";
+
 constexpr std::string_view media_css = R"css(
 body{margin:0;background:#000}
 .odr-media{display:flex;align-items:center;justify-content:center;min-height:100vh}
@@ -185,6 +262,11 @@ mark{background:#ff0}
 mark.current{background:orange}
 )css";
 
+/// The mark keeps its yellow; only the text on it turns over.
+constexpr std::string_view search_dark_css = R"css(
+mark{color:#0d1117!important}
+)css";
+
 constexpr std::string_view document_js = R"js(
 (function () {
   "use strict";
@@ -1100,18 +1182,32 @@ struct Asset {
 
 constexpr Asset document_css_asset{HtmlResourceType::css, "text/css",
                                    "document.css", document_css};
+constexpr Asset document_dark_css_asset{HtmlResourceType::css, "text/css",
+                                        "document-dark.css", document_dark_css};
 constexpr Asset spreadsheet_css_asset{HtmlResourceType::css, "text/css",
                                       "spreadsheet.css", spreadsheet_css};
+constexpr Asset spreadsheet_dark_css_asset{HtmlResourceType::css, "text/css",
+                                           "spreadsheet-dark.css",
+                                           spreadsheet_dark_css};
 constexpr Asset text_css_asset{HtmlResourceType::css, "text/css", "text.css",
                                text_css};
+constexpr Asset text_dark_css_asset{HtmlResourceType::css, "text/css",
+                                    "text-dark.css", text_dark_css};
 constexpr Asset xml_css_asset{HtmlResourceType::css, "text/css", "xml.css",
                               xml_css};
+constexpr Asset xml_dark_css_asset{HtmlResourceType::css, "text/css",
+                                   "xml-dark.css", xml_dark_css};
 constexpr Asset filesystem_css_asset{HtmlResourceType::css, "text/css",
                                      "filesystem.css", filesystem_css};
+constexpr Asset filesystem_dark_css_asset{HtmlResourceType::css, "text/css",
+                                          "filesystem-dark.css",
+                                          filesystem_dark_css};
 constexpr Asset media_css_asset{HtmlResourceType::css, "text/css", "media.css",
                                 media_css};
 constexpr Asset search_css_asset{HtmlResourceType::css, "text/css",
                                  "search.css", search_css};
+constexpr Asset search_dark_css_asset{HtmlResourceType::css, "text/css",
+                                      "search-dark.css", search_dark_css};
 constexpr Asset document_js_asset{HtmlResourceType::js, "text/javascript",
                                   "document.js", document_js};
 constexpr Asset search_js_asset{HtmlResourceType::js, "text/javascript",
@@ -1142,19 +1238,40 @@ HtmlResources locate_all(const std::span<const Asset> assets,
   return resources;
 }
 
-void write_style(const Asset &asset, const WritingState &state) {
+/// Adds the dark sheets where the config asks for them.
+HtmlResources locate_all(const std::span<const Asset> assets,
+                         const std::span<const Asset> dark,
+                         const HtmlConfig &config) {
+  HtmlResources resources = locate_all(assets, config);
+  if (writes_dark_style(config)) {
+    for (const Asset &asset : dark) {
+      locate(asset, config, resources);
+    }
+  }
+  return resources;
+}
+
+/// @p media, when given, gates the stylesheet on that media query.
+void write_style(const Asset &asset, const WritingState &state,
+                 const std::string_view media = {}) {
   if (const HtmlResourceLocation location =
           locate(asset, state.config(), state.resources());
       location.has_value()) {
-    state.out().write_header_style(escape_attribute(*location));
+    state.out().write_header_style(escape_attribute(*location), media);
     return;
   }
 
-  state.out().write_header_style_begin();
+  state.out().write_header_style_begin(media);
   state.out().out() << asset.content;
   state.out().write_header_style_end();
 }
 
+void write_dark_style(const Asset &asset, const WritingState &state) {
+  if (writes_dark_style(state.config())) {
+    write_style(asset, state, dark_style_media(state.config()));
+  }
+}
+
 void write_script(const Asset &asset, const WritingState &state) {
   if (const HtmlResourceLocation location =
           locate(asset, state.config(), state.resources());
@@ -1174,6 +1291,16 @@ void write_script(const Asset &asset, const WritingState &state) {
 
 namespace odr::internal {
 
+bool html::writes_dark_style(const HtmlConfig &config) {
+  return config.color_scheme != HtmlColorScheme::light;
+}
+
+std::string_view html::dark_style_media(const HtmlConfig &config) {
+  return config.color_scheme == HtmlColorScheme::system
+             ? "(prefers-color-scheme: dark)"
+             : "";
+}
+
 void html::write_document_style(const WritingState &state) {
   write_style(document_css_asset, state);
 }
@@ -1182,18 +1309,38 @@ void html::write_spreadsheet_style(const WritingState &state) {
   write_style(spreadsheet_css_asset, state);
 }
 
+void html::write_document_dark_style(const WritingState &state) {
+  write_dark_style(document_dark_css_asset, state);
+}
+
+void html::write_spreadsheet_dark_style(const WritingState &state) {
+  write_dark_style(spreadsheet_dark_css_asset, state);
+}
+
 void html::write_text_style(const WritingState &state) {
   write_style(text_css_asset, state);
 }
 
+void html::write_text_dark_style(const WritingState &state) {
+  write_dark_style(text_dark_css_asset, state);
+}
+
 void html::write_xml_style(const WritingState &state) {
   write_style(xml_css_asset, state);
 }
 
+void html::write_xml_dark_style(const WritingState &state) {
+  write_dark_style(xml_dark_css_asset, state);
+}
+
 void html::write_filesystem_style(const WritingState &state) {
   write_style(filesystem_css_asset, state);
 }
 
+void html::write_filesystem_dark_style(const WritingState &state) {
+  write_dark_style(filesystem_dark_css_asset, state);
+}
+
 void html::write_media_style(const WritingState &state) {
   write_style(media_css_asset, state);
 }
@@ -1202,6 +1349,10 @@ void html::write_search_style(const WritingState &state) {
   write_style(search_css_asset, state);
 }
 
+void html::write_search_dark_style(const WritingState &state) {
+  write_dark_style(search_dark_css_asset, state);
+}
+
 void html::write_document_script(const WritingState &state) {
   write_script(document_js_asset, state);
 }
@@ -1221,13 +1372,15 @@ void html::write_text_script(const WritingState &state) {
 HtmlResources html::locate_text_resources(const HtmlConfig &config) {
   static constexpr std::array assets{text_css_asset, search_css_asset,
                                      search_js_asset, text_js_asset};
-  return locate_all(assets, config);
+  static constexpr std::array dark{text_dark_css_asset, search_dark_css_asset};
+  return locate_all(assets, dark, config);
 }
 
 HtmlResources html::locate_xml_resources(const HtmlConfig &config) {
   static constexpr std::array assets{xml_css_asset, search_css_asset,
                                      search_js_asset};
-  return locate_all(assets, config);
+  static constexpr std::array dark{xml_dark_css_asset, search_dark_css_asset};
+  return locate_all(assets, dark, config);
 }
 
 HtmlResources html::locate_search_resources(const HtmlConfig &config) {
diff --git a/src/odr/internal/html/frontend.hpp b/src/odr/internal/html/frontend.hpp
index 5d2c8ba99..f0047335f 100644
--- a/src/odr/internal/html/frontend.hpp
+++ b/src/odr/internal/html/frontend.hpp
@@ -2,6 +2,8 @@
 
 #include <odr/html.hpp>
 
+#include <string_view>
+
 namespace odr::internal::html {
 
 struct WritingState;
@@ -9,15 +11,30 @@ struct WritingState;
 /// Each of these writes one complete `<style>`/`<script>` element, or links it
 /// as a shipped @ref odr::HtmlResource when the config asks for that.
 
+/// Each `write_*_dark_style` follows the style it restates and writes nothing
+/// for @ref odr::HtmlColorScheme::light.
+
 void write_document_style(const WritingState &state);
+void write_document_dark_style(const WritingState &state);
 /// Written in addition to the document style.
 void write_spreadsheet_style(const WritingState &state);
+void write_spreadsheet_dark_style(const WritingState &state);
 void write_text_style(const WritingState &state);
+void write_text_dark_style(const WritingState &state);
 void write_xml_style(const WritingState &state);
+void write_xml_dark_style(const WritingState &state);
 void write_filesystem_style(const WritingState &state);
+void write_filesystem_dark_style(const WritingState &state);
+/// Black in every scheme, so no dark style.
 void write_media_style(const WritingState &state);
 /// Written by every view that writes the search script.
 void write_search_style(const WritingState &state);
+void write_search_dark_style(const WritingState &state);
+
+/// For a view writing its style inline: whether to write a dark one, and the
+/// `media` gating it — empty for @ref odr::HtmlColorScheme::dark.
+bool writes_dark_style(const HtmlConfig &config);
+std::string_view dark_style_media(const HtmlConfig &config);
 
 /// The `odr` object a document view exposes to its host: `generateDiff()`.
 void write_document_script(const WritingState &state);
diff --git a/src/odr/internal/html/html_writer.cpp b/src/odr/internal/html/html_writer.cpp
index bcb68fb24..0ef852a0b 100644
--- a/src/odr/internal/html/html_writer.cpp
+++ b/src/odr/internal/html/html_writer.cpp
@@ -192,19 +192,28 @@ void HtmlWriter::write_header_charset(const std::string &charset) {
   out() << "\"/>";
 }
 
-void HtmlWriter::write_header_style(const std::string &href) {
+void HtmlWriter::write_header_style(const std::string &href,
+                                    const std::string_view media) {
   write_new_line();
 
   out() << R"(<link rel="stylesheet" href=")";
   out() << href;
-  out() << "\"/>";
+  out() << "\"";
+  if (!media.empty()) {
+    out() << R"( media=")" << media << "\"";
+  }
+  out() << "/>";
 }
 
-void HtmlWriter::write_header_style_begin() {
+void HtmlWriter::write_header_style_begin(const std::string_view media) {
   write_new_line();
   ++m_current_indent;
 
-  out() << "<style>";
+  out() << "<style";
+  if (!media.empty()) {
+    out() << R"( media=")" << media << "\"";
+  }
+  out() << ">";
 }
 
 void HtmlWriter::write_header_style_end() {
diff --git a/src/odr/internal/html/html_writer.hpp b/src/odr/internal/html/html_writer.hpp
index b26713d02..88068c0fc 100644
--- a/src/odr/internal/html/html_writer.hpp
+++ b/src/odr/internal/html/html_writer.hpp
@@ -5,6 +5,7 @@
 #include <functional>
 #include <iosfwd>
 #include <string>
+#include <string_view>
 #include <variant>
 #include <vector>
 
@@ -61,8 +62,9 @@ class HtmlWriter {
   void write_header_viewport(const std::string &viewport);
   void write_header_target(const std::string &target);
   void write_header_charset(const std::string &charset);
-  void write_header_style(const std::string &href);
-  void write_header_style_begin();
+  /// @p media, when given, gates the stylesheet on that media query.
+  void write_header_style(const std::string &href, std::string_view media = {});
+  void write_header_style_begin(std::string_view media = {});
   void write_header_style_end();
 
   void write_script(const std::string &src);
diff --git a/src/odr/internal/html/image_file.cpp b/src/odr/internal/html/image_file.cpp
index 9a4cd355d..6b2ad7f7b 100644
--- a/src/odr/internal/html/image_file.cpp
+++ b/src/odr/internal/html/image_file.cpp
@@ -7,6 +7,7 @@
 
 #include <odr/internal/common/file.hpp>
 #include <odr/internal/html/common.hpp>
+#include <odr/internal/html/frontend.hpp>
 #include <odr/internal/html/html_service.hpp>
 #include <odr/internal/html/html_writer.hpp>
 #include <odr/internal/svm/svm_file.hpp>
@@ -107,6 +108,11 @@ class HtmlServiceImpl final : public HtmlService {
     out.write_header_style_begin();
     out.out() << "body{margin:0;background:#fff}";
     out.write_header_style_end();
+    if (writes_dark_style(config())) {
+      out.write_header_style_begin(dark_style_media(config()));
+      out.out() << ":root{color-scheme:dark}body{background:#0d1117}";
+      out.write_header_style_end();
+    }
     out.write_header_end();
 
     out.write_body_begin();
diff --git a/src/odr/internal/html/text_file.cpp b/src/odr/internal/html/text_file.cpp
index bf778d30e..4f1ceacb1 100644
--- a/src/odr/internal/html/text_file.cpp
+++ b/src/odr/internal/html/text_file.cpp
@@ -101,7 +101,9 @@ class HtmlServiceImpl final : public HtmlService {
     write_viewport_meta(out, config(), false);
 
     write_text_style(state);
+    write_text_dark_style(state);
     write_search_style(state);
+    write_search_dark_style(state);
 
     out.write_header_end();
 
diff --git a/src/odr/internal/html/xml_file.cpp b/src/odr/internal/html/xml_file.cpp
index 225099862..6cc6a9ebd 100644
--- a/src/odr/internal/html/xml_file.cpp
+++ b/src/odr/internal/html/xml_file.cpp
@@ -261,7 +261,9 @@ class HtmlServiceImpl final : public HtmlService {
     write_viewport_meta(out, config(), false);
 
     write_xml_style(state);
+    write_xml_dark_style(state);
     write_search_style(state);
+    write_search_dark_style(state);
 
     out.write_header_end();
 
diff --git a/test/src/html_test.cpp b/test/src/html_test.cpp
index 89331af1a..5cddf632d 100644
--- a/test/src/html_test.cpp
+++ b/test/src/html_test.cpp
@@ -1,3 +1,4 @@
+#include <algorithm>
 #include <filesystem>
 #include <fstream>
 #include <sstream>
@@ -140,6 +141,106 @@ TEST(html, archive_listing) {
       "10000000000001F4000001FF1D2394A8.jpg"));
 }
 
+namespace {
+
+std::string render(const std::string &path, const HtmlConfig &config) {
+  const DecodedFile file(TestData::test_file_path(path), Logger::null());
+
+  std::ostringstream out;
+  html::translate(file, config).list_views().at(0).write_html(out);
+  return out.str();
+}
+
+std::string render_odt(const HtmlConfig &config) {
+  return render("odr-public/odt/about.odt", config);
+}
+
+} // namespace
+
+// Reflowed to the viewport there is no page box to inset the text.
+TEST(html, flowing_text_is_inset_from_the_screen_edge) {
+  HtmlConfig config;
+  config.text_document_margin = false;
+
+  const std::string page = render_odt(config);
+
+  EXPECT_NE(page.find(R"(<div class="odr-text-flow">)"), std::string::npos);
+  EXPECT_NE(page.find(".odr-text-flow{padding:"), std::string::npos);
+}
+
+// For `system` it is the element carrying the dark style that is gated, not a
+// rule inside it.
+TEST(html, color_scheme_writes_the_dark_style) {
+  HtmlConfig config;
+
+  EXPECT_EQ(config.color_scheme, HtmlColorScheme::light);
+  EXPECT_EQ(render_odt(config).find("color-scheme:dark"), std::string::npos);
+
+  config.color_scheme = HtmlColorScheme::dark;
+  const std::string dark = render_odt(config);
+  EXPECT_NE(dark.find("color-scheme:dark"), std::string::npos);
+  EXPECT_EQ(dark.find("prefers-color-scheme"), std::string::npos);
+
+  config.color_scheme = HtmlColorScheme::system;
+  const std::string system = render_odt(config);
+  EXPECT_NE(
+      system.find(R"html(<style media="(prefers-color-scheme: dark)">)html"),
+      std::string::npos);
+}
+
+// A linked stylesheet keeps its media query, and the service answers for it.
+TEST(html, linked_dark_style_is_served) {
+  HtmlConfig config;
+  config.embed_shipped_resources = false;
+  config.color_scheme = HtmlColorScheme::system;
+
+  const DecodedFile file(TestData::test_file_path("odr-public/odt/about.odt"),
+                         Logger::null());
+  const HtmlService service = html::translate(file, config);
+
+  std::ostringstream out;
+  const HtmlResources resources = service.list_views().at(0).write_html(out);
+
+  EXPECT_NE(
+      out.str().find(
+          R"html(<link rel="stylesheet" href="document-dark.css" media="(prefers-color-scheme: dark)"/>)html"),
+      std::string::npos);
+  EXPECT_TRUE(std::ranges::any_of(resources, [](const auto &entry) {
+    return entry.second.has_value() && *entry.second == "document-dark.css";
+  }));
+  EXPECT_TRUE(service.exists("document-dark.css"));
+}
+
+// Every view but the pdf one turns over.
+TEST(html, color_scheme_reaches_every_view) {
+  HtmlConfig config;
+  config.color_scheme = HtmlColorScheme::dark;
+
+  // a text file, and the gutter it numbers its lines in
+  const std::string text = render("odr-public/txt/lorem ipsum.txt", config);
+  EXPECT_NE(text.find("--odr-text-gutter:#161b22"), std::string::npos);
+
+  // a source view
+  const DecodedFile xml_file(File::from_memory("<a><b>c</b></a>"),
+                             FileType::xml);
+  std::ostringstream xml;
+  html::translate(xml_file, config).list_views().at(0).write_html(xml);
+  EXPECT_NE(xml.str().find("--odr-xml-name:#7ee787"), std::string::npos);
+
+  // a file listing: the archive view of a zip
+  const DecodedFile archive(
+      TestData::test_file_path("odr-public/odt/about.odt"), FileType::zip,
+      Logger::null());
+  std::ostringstream listing;
+  html::translate(archive, config).list_views().at(0).write_html(listing);
+  EXPECT_NE(listing.str().find("--odr-files-link:#6cb6ff"), std::string::npos);
+
+  // the search mark turns its text over wherever a view paints one
+  EXPECT_NE(text.find("mark{color:#0d1117!important}"), std::string::npos);
+  EXPECT_NE(listing.str().find("mark{color:#0d1117!important}"),
+            std::string::npos);
+}
+
 TEST(html, views) {
   const auto logger = Logger::create_stdio("odr-test", LogLevel::verbose);
 
diff --git a/test/src/odr_test.cpp b/test/src/odr_test.cpp
index fd91eb55d..11bd2d6e8 100644
--- a/test/src/odr_test.cpp
+++ b/test/src/odr_test.cpp
@@ -1,6 +1,7 @@
 #include <odr/document.hpp>
 #include <odr/exceptions.hpp>
 #include <odr/file.hpp>
+#include <odr/html.hpp>
 #include <odr/odr.hpp>
 
 #include <test_util.hpp>
@@ -8,6 +9,7 @@
 #include <algorithm>
 #include <optional>
 #include <set>
+#include <sstream>
 #include <string>
 #include <string_view>
 #include <vector>
@@ -155,6 +157,56 @@ TEST(FileTypeTable, capabilities_build_on_each_other) {
     if (capabilities.edit) {
       EXPECT_TRUE(capabilities.save) << file_type_to_string(type);
     }
+    if (!capabilities.translate_html) {
+      EXPECT_FALSE(capabilities.color_scheme) << file_type_to_string(type);
+    }
+  }
+}
+
+/// Holds the declared `color_scheme` against what the renderer emits.
+TEST(FileTypeCapabilities, color_scheme_matches_the_html) {
+  const auto &logger = Logger::null();
+
+  for (const FileType type : every_file_type()) {
+    const FileTypeCapabilities declared = capabilities_by_file_type(type);
+    if (!declared.translate_html) {
+      continue;
+    }
+
+    const std::vector<TestFile> test_files = TestData::test_files(type);
+    if (test_files.empty() || test_files.front().password.has_value()) {
+      continue;
+    }
+
+    std::optional<DecodedFile> file;
+    try {
+      file = open(test_files.front().absolute_path, type, logger);
+    } catch (...) {
+      continue;
+    }
+
+    const auto render = [&](const HtmlColorScheme scheme) {
+      HtmlConfig config;
+      config.color_scheme = scheme;
+      // one page of a pdf is enough, and the rest is slow
+      config.page_range_end = 1;
+
+      std::ostringstream out;
+      html::translate(*file, config).list_views().at(0).write_html(out);
+      return out.str();
+    };
+
+    std::string light;
+    std::string dark;
+    try {
+      light = render(HtmlColorScheme::light);
+      dark = render(HtmlColorScheme::dark);
+    } catch (...) {
+      continue;
+    }
+
+    EXPECT_EQ(light != dark, declared.color_scheme)
+        << file_type_to_string(type) << " " << test_files.front().short_path;
   }
 }
 
diff --git a/wasm/js/index.d.ts b/wasm/js/index.d.ts
index 261f1889e..d2e3de296 100644
--- a/wasm/js/index.d.ts
+++ b/wasm/js/index.d.ts
@@ -7,6 +7,7 @@ export interface EnumTables {
   FileCategory: Record<string, number>;
   DocumentType: Record<string, number>;
   HtmlResourceType: Record<string, number>;
+  HtmlColorScheme: Record<string, number>;
   HtmlTableGridlines: Record<string, number>;
   HtmlViewportMode: Record<string, number>;
   PdfTextMode: Record<string, number>;
@@ -19,6 +20,8 @@ export interface Capabilities {
   open: boolean;
   decrypt: boolean;
   translateHtml: boolean;
+  /** The view this type renders as honors `HtmlConfig.colorScheme`. */
+  colorScheme: boolean;
   edit: boolean;
   save: boolean;
   encrypt: boolean;
@@ -77,6 +80,7 @@ export interface HtmlConfig {
   backgroundImageDpi?: number;
   pageRangeBegin?: number;
   pageRangeEnd?: number;
+  colorScheme?: number;
   spreadsheetGridlines?: number;
   viewportMode?: number;
   pdfTextMode?: number;
diff --git a/wasm/src/odr_wasm.cpp b/wasm/src/odr_wasm.cpp
index 1c9f09411..4cc983a5e 100644
--- a/wasm/src/odr_wasm.cpp
+++ b/wasm/src/odr_wasm.cpp
@@ -118,6 +118,7 @@ emscripten::val to_capabilities(const FileTypeCapabilities &capabilities) {
   result.set("open", capabilities.open);
   result.set("decrypt", capabilities.decrypt);
   result.set("translateHtml", capabilities.translate_html);
+  result.set("colorScheme", capabilities.color_scheme);
   result.set("edit", capabilities.edit);
   result.set("save", capabilities.save);
   result.set("encrypt", capabilities.encrypt);
diff --git a/wasm/src/wasm_core.cpp b/wasm/src/wasm_core.cpp
index 5b1861587..ff0ff5eb8 100644
--- a/wasm/src/wasm_core.cpp
+++ b/wasm/src/wasm_core.cpp
@@ -103,6 +103,10 @@ emscripten::val enum_tables() {
              table(entry("none", HtmlTableGridlines::none),
                    entry("soft", HtmlTableGridlines::soft),
                    entry("hard", HtmlTableGridlines::hard)));
+  result.set("HtmlColorScheme",
+             table(entry("light", HtmlColorScheme::light),
+                   entry("dark", HtmlColorScheme::dark),
+                   entry("system", HtmlColorScheme::system)));
   result.set("HtmlViewportMode",
              table(entry("automatic", HtmlViewportMode::automatic),
                    entry("fit_width", HtmlViewportMode::fit_width),
diff --git a/wasm/src/wasm_html.cpp b/wasm/src/wasm_html.cpp
index 2914338db..416553483 100644
--- a/wasm/src/wasm_html.cpp
+++ b/wasm/src/wasm_html.cpp
@@ -138,6 +138,7 @@ HtmlConfig to_html_config(const emscripten::val &value) {
     config.page_range_end = end.as<std::uint32_t>();
   }
 
+  read_enum(value, "colorScheme", config.color_scheme);
   read_enum(value, "spreadsheetGridlines", config.spreadsheet_gridlines);
   read_enum(value, "viewportMode", config.viewport_mode);
   read_enum(value, "pdfTextMode", config.pdf_text_mode);
diff --git a/wasm/tests/enums.test.mjs b/wasm/tests/enums.test.mjs
index 42c3a7bd4..2966c75bb 100644
--- a/wasm/tests/enums.test.mjs
+++ b/wasm/tests/enums.test.mjs
@@ -18,6 +18,7 @@ const pinned = {
     font: 4,
     media: 5,
   },
+  HtmlColorScheme: { light: 0, dark: 1, system: 2 },
   HtmlTableGridlines: { none: 0, soft: 1, hard: 2 },
   HtmlViewportMode: {
     automatic: 0,
diff --git a/wasm/tests/smoke.test.mjs b/wasm/tests/smoke.test.mjs
index 8dec6820a..703accc6e 100644
--- a/wasm/tests/smoke.test.mjs
+++ b/wasm/tests/smoke.test.mjs
@@ -64,8 +64,14 @@ describe('smoke', () => {
     assert.ok(odt.extensions.includes('odt'));
     assert.ok(odt.mimeTypes.includes('application/vnd.oasis.opendocument.text'));
     assert.equal(odt.capabilities.translateHtml, true);
+    assert.equal(odt.capabilities.colorScheme, true);
     assert.equal(odt.capabilities.open, true);
 
+    // a pdf renders, but paints its own page backgrounds
+    const pdf = types.find((t) => t.name === 'pdf');
+    assert.equal(pdf.capabilities.translateHtml, true);
+    assert.equal(pdf.capabilities.colorScheme, false);
+
     // both tables are always present, so a caller may concatenate without
     // checking
     for (const type of types) {