Mocha 12

Mocha 12 (sometimes “v12”) is an upcoming release of Mocha which updates internal dependencies while maintaining a stable end-user experience. There are no planned breaking changes between Mocha 11 and Mocha 12.

We released 11 unique betas through early April 2026, and I was personally aiming for a release candidate in early April and a full release in late April. However, I got super sick.

Once I’m healthy, the plan is simple:

1. Document breaking changes
2. Open one last PR to migrate from CJS to ESM
3. Review unrelated pending PRs while I wait
4. Once we’re converted to ESM, release the first Mocha 12 release candidate (12.0.0-rc.1)
5. Iteratively fix bugs, but no new features in any release candidates
6. Once we’re confident in stability, release Mocha 12!

Dates and times are PDT (UTC-7). All links are to GitHub unless otherwise specified.

Remaining work

Items are ordered by ascending creation time.

• #5025: Bug: remove util.inherits / convert to classes
  • I re-opened this on 2026-04-18 because the PR to update the docs wasn’t correct
    • #5677: docs: switch util.inherits to class extends
• #5357: Mocha 12 Release Plan
  • I asked about necessary docs on 2026-03-26
  • I started drafting #5848: chore: add v12 release notes on 2026-04-02
• #5400: Repo: Switch from CJS to ESM internally
  • Mostafa volunteered to do this, and I gave him the green light to open one big PR on 2026-04-28

References

• 2026-02-21 - Major releases (MAINTAINERS.md)
• Mocha v12.0.0 milestone

See also Mocha - markwiemer.com