The ParserMigration extension was deployed during 2018 to compare legacy Tidy-based output with the Remex-based replacement, to aid in migration to the new tidy algorithm. It was undeployed after that migration was complete.
It was overhauled in 2023 to compare Parsoid output with the legacy wikitext parser output (T333177), as part of the #parsoid-read-views project, and the #content-transform-team would like to redeploy it to production.
The [README](https://github.com/wikimedia/mediawiki-extensions-ParserMigration/blob/master/README.md) and on-wiki [Help:Extension:ParserMigration](https://www.mediawiki.org/wiki/Help:Extension:ParserMigration) provide more information on the operation and purpose of this extension.
**Testing ParserMigration**
You can follow the instructions at [Help:Extension:ParserMigration](https://www.mediawiki.org/wiki/Help:Extension:ParserMigration) to enable the user preference and then view the side-by-side comparison output of (for example) the Main Page.
Special:ApiSandbox can also be used to verify that the action API component is working: `action=parser-migration`.
**Needed for deployment of the ParserMigration extension**
[] Security Review: this was presumably done for the 2018 deployment and just requires an update
[] Design Review: this is intended primarily for internal use
[] Performance Review: part of the purpose of deploying this extension is to allow #content-transform-team to benchmark Parsoid rendering under realistic conditions for production read views
[] Deploy on beta sites
[] Deploy on test wikis
[] Deploy on all wikis