Hello, technical contributors!

The MediaWiki Interfaces team is deprecating XSLT stylesheets within the Action API.

Support for the format=xml&*xlst={stylesheet}* will be removed from Wikimedia projects by the end of November, 2025. In addition, it will soon be disabled by default in MediaWiki release versions: v1.43 (LTS), v1.44, and v1.45. Support for XSLT stylesheets will be fully removed from MediaWiki v1.46 (expected to release between April and May 2026).

*=== Why are we deprecating and removing this capability? ===* Support for XSLT is generally being removed from browsers, due to a high rate of security risks and declining usage. Chrome is officially starting the XSLT deprecation cycle https://developer.chrome.com/docs/web-platform/deprecating-xsltin November 2025, with full removal expected by November 2026. Other browsers are expected to follow. To ensure that we are not including a feature that will no longer be supported by browsers, we decided to end support, as well.

*=== What is the impact? === * There is currently very limited adoption of this feature across Wikimedia projects, with usage limited to a handful of gadgets that currently rely on this capability. We are engaging with some of the key gadget owners directly, so they are aware of the change and can adjust or remove lesser used features accordingly.

We also recognize that some third parties may rely on XSLT stylesheets. In this case, we encourage consumers to find alternative solutions as soon as possible, given the end of XSLT support goes beyond the scope of MediaWiki.

I encourage tool developers, gadget authors, and third party users to engage directly if you have questions, concerns, or if this change may block your ability to upgrade to future versions in a timely manner.

Thanks, Halley

*Halley Coplin* (she/her) Sr. Product Manager, MediaWiki Interfaces Wikimedia Foundation https://wikimediafoundation.org/