T288161: Enable CodeMirror's Syntax Highlighting on English Wikipedia by default has as of October 2026 been live for several weeks, and to my knowledge we haven't received any complaints. The next natural step is to enable it by default on all wikis.
I'm not certain how much a global RfC will bring us. Such an RfC would not be advertised to the unregistered users who are actually affected. The only opposition we saw in the original 2021 RfC on English Wikipedia was because of performance, and that has largely been resolved now with the upgrade to CodeMirror 6, and the recent optimizations to the 2017 editor implementation (T432558). Our 2026 follow-up straw proposal saw no opposition. It seems users are generally content with it, provided they have a way to turn it off when needed.
We should give this a try and enable it everywhere by default, and just as with T288161, we'd only do this for new accounts and logged out users.
Even if we decide not to do this for the WMF cluster, I think we should have it enabled by default in the extension. It's already kind of weird that the extension ships with everything disabled. Let's get that done at least in time for MW 1.47.
Proposed changes
- Set $wgConditionalUserOptions['usecodemirror'] on the WMF cluster, targeting only logged out users and users created after the date the config change is deployed.
- Enwiki's conditional should stay at the date the same change was made there, 2026-09-14
- Set the default value of the usecodemirror preference to 1 in extension.json (no effect on WMF cluster)