Firefox 146 support for <meta name=rating> (#42119)

Author: chrisdavidmills

files/en-us/mozilla/firefox/experimental_features/index.md

@@ -746,6 +746,33 @@ The two `security.insecure_connection_text_*` preferences add a "Not secure" tex
 - `browser.urlbar.trimHttps`
   - : Set to `true` to trim the `https:` prefix from address bar URLs.
 
+### Restricting adult content with `<meta name="rating">`
+
+The non-standard [`<meta name="rating">`](/en-US/docs/Web/HTML/Reference/Elements/meta) element can be included on a webpage to denote the page's content as restricted/adult. At the time of writing, there are two possible `content` values, `adult` ([defined by Google](https://developers.google.com/search/docs/specialty/explicit/guidelines#add-metadata)) and `RTA-5042-1996-1400-1577-RTA` ([defined by ASACP](https://www.rtalabel.org/?content=howto#top)), which have the same effect (more options may be added in future).
+
+The following `<meta>` elements are equivalent:
+
+```html
+<meta name="rating" content="adult" />
+<meta name="rating" content="RTA-5042-1996-1400-1577-RTA" />
+```
+
+Browsers that recognise this element can then take steps to restrict users from viewing the content. Firefox's implementation replaces the page with the content found at `about:restricted`, which explains to the user that they are trying to view restricted content, explains why they cannot view it, and gives them a back button to return from whence they came.
+
+See [Firefox bug 1991135](https://bugzil.la/1991135) for more details.
+
+| Release channel   | Version added | Enabled by default? |
+| ----------------- | ------------- | ------------------- |
+| Nightly           | 146           | No                  |
+| Developer Edition | 146           | No                  |
+| Beta              | 146           | No                  |
+| Release           | 146           | No                  |
+
+- `security.restrict_to_adults.always`
+  - : Set to `true` to restrict access to webpages that self-identify as adult by including a `<meta name="rating">` element.
+- `security.restrict_to_adults.respect_platform`
+  - : Set to `true` to restrict access to webpages that self-identify as adult by including a `<meta name="rating">` element only when appropriate parental controls are set on the underlying operating system (for example, the macOS _Content & Privacy_ settings are set to restrict explicit web content).
+
 ### Permissions Policy / Feature policy
 
 [Permissions Policy](/en-US/docs/Web/HTTP/Guides/Permissions_Policy) allows web developers to selectively enable, disable, and modify the behavior of certain features and APIs in the browser. It is similar to CSP but controls features instead of security behavior.

files/en-us/mozilla/firefox/releases/146/index.md

@@ -122,6 +122,11 @@ These features are shipping in Firefox 146 but are disabled by default.
 To experiment with them, search for the appropriate preference on the `about:config` page and set it to `true`.
 You can find more such features on the [Experimental features](/en-US/docs/Mozilla/Firefox/Experimental_features) page.
 
+- **`<meta name="rating">`** (Nightly): `security.restrict_to_adults.always` and `security.restrict_to_adults.respect_platform`
+
+  The `<meta name="rating">` element allows websites to self-identify as restricted/adult content. Browsers that recognise this element can then take steps to restrict users from viewing the content. See [Restricting adult content with `<meta name="rating">`](/en-US/docs/Mozilla/Firefox/Experimental_features#restricting_adult_content_with_meta_namerating) for more details.
+  ([Firefox bug 1991135](https://bugzil.la/1991135)).
+
 - **Navigation API** (Nightly): `dom.navigation.webidl.enabled`
 
   Nightly builds now support the Navigation API, which provides the ability to initiate, intercept, and manage browser navigation actions. It can also examine an application's history entries. This is a successor to previous web platform features such as the {{domxref("History API", "", "", "nocode")}} and {{domxref("window.location")}}, which solves their shortcomings and is specifically aimed at the needs of {{glossary("SPA", "single-page applications (SPAs)")}}.