ST-2026-229 · Runtimes & developer platforms
Cloudflare Workers updates its V8 runtime to version 15.3
Cloudflare's Workers changelog records a runtime-engine update to V8 version 15.3 on 28 August 2026.
Previous state
Cloudflare Workers was running the previously documented V8 runtime version 15.2.
Current state
Cloudflare states that the Workers runtime has been updated to V8 version 15.3.
Affected users
Who needs to care
Developers operating Cloudflare Workers code on the managed Workers runtime.
Required response
What to do
Include V8 15.3 in runtime compatibility testing for Workers applications and investigate any application-specific differences before attributing behaviour changes to the engine update.
Evidence boundary
What the source does not prove
Cloudflare proves only the Workers V8 engine version transition to 15.3. It does not state a breaking change, compatibility-date transition, or application-level behaviour change caused by the update.
Lifecycle history
Dated event sequence
- V8 15.2 documented
Cloudflare's Workers changelog records the prior runtime update to V8 15.2.
- V8 15.3 documented
Cloudflare's Workers changelog records the runtime update to V8 15.3.
Evidence ledger
First-party sources
- 01Cloudflare — Workers Changelog
Official Cloudflare Workers documentation · 2026-08-28
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