Tweet by KentonVarda
April 23, 2026
Nitpick: It's not quite correct to say that using an old compatibility date means using an old "version" of the runtime. When hosted on Cloudflare, you are always using the latest version, but the flags tell it to emulate old versions in certain respects. Note that API changes that aren't breaking aren't gated by flags, so even if you have a 2019 compatibility date on your Worker, it will still be able to see lots of new APIs that were introduced since then -- just not the (usually minor) breaking changes.
- Author
- KentonVarda
- Date
- April 23, 2026
- Canonical URL
- /tweets/kentonvarda-2047428696294789294-672bc6