diff --git a/files/en-us/mozilla/add-ons/webextensions/manifest.json/dark_theme/index.md b/files/en-us/mozilla/add-ons/webextensions/manifest.json/dark_theme/index.md
new file mode 100644
index 000000000000000..436a58a9d2917b5
--- /dev/null
+++ b/files/en-us/mozilla/add-ons/webextensions/manifest.json/dark_theme/index.md
@@ -0,0 +1,69 @@
+---
+title: dark_theme
+slug: Mozilla/Add-ons/WebExtensions/manifest.json/dark_theme
+page-type: webextension-manifest-key
+browser-compat: webextensions.manifest.dark_theme
+---
+
+{{AddonSidebar}}
+
+<table class="fullwidth-table standard-table">
+  <tbody>
+    <tr>
+      <th scope="row">Type</th>
+      <td><code>Object</code></td>
+    </tr>
+    <tr>
+      <th scope="row">Optional</th>
+      <td>No</td>
+    </tr>
+    <tr>
+      <th scope="row">Manifest version</th>
+      <td>2 or higher</td>
+    </tr>
+    <tr>
+      <th scope="row">Example</th>
+      <td>
+        <pre class="brush: json">
+"dark_theme": {
+  "images": {
+    "theme_frame": "images/moon.jpg"
+  },
+  "colors": {
+    "frame": "#CF723F",
+    "tab_background_text": "#000"
+  }
+}</pre
+        >
+      </td>
+    </tr>
+  </tbody>
+</table>
+
+Use the `dark_theme` key to define a static theme to apply when Firefox is using the dark color scheme. The `dark_theme` key uses the same syntax and supports the same image, color, and property objects as the `theme` key.
+
+See the [`theme` key](/en-US/docs/Mozilla/Add-ons/WebExtensions/manifest.json/theme) for more information.
+
+## Browser compatibility
+
+{{Compat}}
+
+### Chrome compatibility
+
+In Chrome:
+
+- `colors/toolbar_text` is not used, use `colors/bookmark_text` instead.
+- `images/theme_frame` anchors the image to the top left of the header and if the image doesn't fill the header area tile the image.
+- all colors must be specified as an array of RGB values, like this:
+
+  ```json
+  "theme": {
+    "colors": {
+       "frame": [255, 0, 0],
+       "tab_background_text": [0, 255, 0],
+       "bookmark_text": [0, 0, 255]
+    }
+  }
+  ```
+
+  The array form and the CSS color form are accepted for all properties.
diff --git a/files/en-us/mozilla/add-ons/webextensions/manifest.json/index.md b/files/en-us/mozilla/add-ons/webextensions/manifest.json/index.md
index 2e20b4f0b91c8da..54732da40a2928c 100644
--- a/files/en-us/mozilla/add-ons/webextensions/manifest.json/index.md
+++ b/files/en-us/mozilla/add-ons/webextensions/manifest.json/index.md
@@ -30,6 +30,7 @@ These are the `manifest.json` keys; these keys are available in Manifest V2 and
 - [commands](/en-US/docs/Mozilla/Add-ons/WebExtensions/manifest.json/commands)
 - [content_scripts](/en-US/docs/Mozilla/Add-ons/WebExtensions/manifest.json/content_scripts)
 - [content_security_policy](/en-US/docs/Mozilla/Add-ons/WebExtensions/manifest.json/content_security_policy)
+- [dark_theme](/en-US/docs/Mozilla/Add-ons/WebExtensions/manifest.json/dark_theme)
 - [declarative_net_request](/en-US/docs/Mozilla/Add-ons/WebExtensions/manifest.json/declarative_net_request)
 - [default_locale](/en-US/docs/Mozilla/Add-ons/WebExtensions/manifest.json/default_locale)
 - [description](/en-US/docs/Mozilla/Add-ons/WebExtensions/manifest.json/description)
diff --git a/files/en-us/mozilla/add-ons/webextensions/manifest.json/theme/index.md b/files/en-us/mozilla/add-ons/webextensions/manifest.json/theme/index.md
index 57545f73a5e8dc7..720eca668ef181c 100644
--- a/files/en-us/mozilla/add-ons/webextensions/manifest.json/theme/index.md
+++ b/files/en-us/mozilla/add-ons/webextensions/manifest.json/theme/index.md
@@ -40,7 +40,7 @@ browser-compat: webextensions.manifest.theme
   </tbody>
 </table>
 
-Use the theme key to define a static theme to apply to Firefox.
+Use the `theme` key to define a static theme to apply to Firefox. When provided alone, this defines the theme used when Firefox is using either the light or dark color schemes. If the [`dark_theme` key](/en-US/docs/Mozilla/Add-ons/WebExtensions/manifest.json/dark_theme) key is provided, this key provides the theme used when Firefox is using the light color scheme.
 
 > [!NOTE]
 > If you want to include a theme with an extension, please see the {{WebExtAPIRef("theme")}} API.
diff --git a/files/en-us/mozilla/firefox/releases/68/index.md b/files/en-us/mozilla/firefox/releases/68/index.md
index 114a4bbeb0cd058..65069ffbb9afef9 100644
--- a/files/en-us/mozilla/firefox/releases/68/index.md
+++ b/files/en-us/mozilla/firefox/releases/68/index.md
@@ -174,7 +174,7 @@ _No changes._
 
 ### Manifest changes
 
-_No changes._
+- Support added for the [`dark_theme` key](/en-US/docs/Mozilla/Add-ons/WebExtensions/manifest.json/dark_theme). This key enables a static theme to define its looks when Firefox is using the dark color scheme ([Firefox bug 1525762](https://bugzil.la/1525762)).
 
 ## See also