Intent to ship: Synchronous initial about:blank
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Vincent Hilla
Nov 20, 2025, 9:39:59 AM (12 days ago) Nov 20
to dev-pl...@mozilla.org
We intend to land synchronous initial about:blank soon in Firefox 147. This is a web-exposed change to align with the web platform.
Summary:
Gecko currently generates a synthetic (non-parser-generated) about:blank document as needed when creating a new browsing context. However, if that context navigates to about:blank, we asynchronously create _another_ about:blank document that replaces the synthetic one and then fires a load event. This is a long-standing Web compat issue because the second document overwrites changes made to the first and affects load timing.
Our change removes the second parser-created about:blank and fires the load event for the synthetic about:blank synchronously if the initial (possibly implicit) navigation URL is about:blank.
Gecko currently generates a synthetic (non-parser-generated) about:blank document as needed when creating a new browsing context. However, if that context navigates to about:blank, we asynchronously create _another_ about:blank document that replaces the synthetic one and then fires a load event. This is a long-standing Web compat issue because the second document overwrites changes made to the first and affects load timing.
Our change removes the second parser-created about:blank and fires the load event for the synthetic about:blank synchronously if the initial (possibly implicit) navigation URL is about:blank.
Bug:
Intent to prototype:
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