Compatibility flags

Projects use Wrangler’s standard compatibility_flags array. The server accepts only flags advertised by extension capabilities and supported by the pinned runtime.

{
  "name": "hello-typescript",
  "main": "src/index.ts",
  "compatibility_date": "2026-09-08",
  "compatibility_flags": []
}

Use Wrangler’s snake_case field names. Internal system flags remain executable identity and are not copied into project configuration.

Topic	Cloudflare	open-compute
Flag names and semantics	Cloudflare compatibility flags	Same names from workerd
Project compatibility_flags	Yes	Persisted and validated per immutable Version
Unsupported flags	Upload fails	Upload fails closed
Live supported set	Dashboard / Wrangler	Extension capabilities and packages/runtime/workerd.lock.json