Per the RfC a while back[1] and the previous announcement,[2] we're about to remove the deprecated dbg, txt, and yaml output formats from the API. This is planned for 1.27.0-wmf.8, which is currently scheduled to be deployed to WMF wikis starting December 1, 2015.[3]

Users using the yaml format should be able to easily change to json, as the format is entirely identical.

This removal may impact some tools. If you know of any tool using these deprecated formats, please encourage them to upgrade before December 1.

[1]: https://www.mediawiki.org/wiki/Requests_for_comment/Ditch_crappy_API_formats [2]: https://lists.wikimedia.org/pipermail/mediawiki-api-announce/2015-July/00009... [3]: https://www.mediawiki.org/wiki/MediaWiki_1.27/Roadmap