diff --git a/files/en-us/mozilla/firefox/releases/139/index.md b/files/en-us/mozilla/firefox/releases/139/index.md
index 1c8edca4ac2c04c..963dfe1edd75e74 100644
--- a/files/en-us/mozilla/firefox/releases/139/index.md
+++ b/files/en-us/mozilla/firefox/releases/139/index.md
@@ -72,6 +72,10 @@ This article provides information about the changes in Firefox 139 that affect d
 
 These features are newly shipped in Firefox 139 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.
 
+- **Prioritized Task Scheduling API** (Nightly release).
+  The [Prioritized Task Scheduling API](/en-US/docs/Web/API/Prioritized_Task_Scheduling_API) provides a standardized way to prioritize all tasks belonging to an application, whether they are defined in a website developer's code, or in third-party libraries and frameworks.
+  This adds support for the {{domxref("scheduler.yield()")}} method and re-enables the whole API in the Nightly release.
+  ([Firefox bug 1958943](https://bugzil.la/1958943), [Firefox bug 1920115](https://bugzil.la/1920115)).
 - **Support for escaping `<` and `>` in attributes when serializing HTML**: `dom.security.html_serialization_escape_lt_gt`.
   Firefox now replaces the `<` and `>` characters with `&lt;` and `&gt;`, respectively, in attributes when serializing HTML. This helps prevent certain exploits where HTML is serialized and then injected back into the DOM.
   The affected methods and properties are: {{domxref("Element.innerHTML")}}, {{domxref("Element.outerHTML")}}, {{domxref("Element.getHTML()")}}, {{domxref("ShadowRoot.innerHTML")}}, and {{domxref("ShadowRoot.getHTML()")}}. ([Firefox bug 1941347](https://bugzil.la/1941347)).