Mock Service Worker vs LocalStack

Free and open source

From $39 per licence/month (Base, billed annually; $45 monthly)

Free and open source. You pay in engineering time and CI minutes.

Plans are Hobby (free, non-commercial), Base $39 and Ultimate $89 per licence/month billed annually, then Enterprise. Commercial use needs a paid licence, and the higher tiers are what unlock advanced IAM enforcement and the wider service coverage.

Everything, self-hosted

Hobby tier is free but explicitly non-commercial, and LocalStack has said the Community emulator will no longer receive product updates.

Category standard

OSS community · since 2020

Category standard

LocalStack · since 2017

• One set of handlers reused across unit, component, E2E and local development.
• Application code is completely unaware it is being mocked — no test-only branches.
• Supports REST and GraphQL with the same model.

• Integration tests against AWS services run offline in seconds at no cloud cost.
• Removes the shared-sandbox-account contention that plagues cloud teams.
• Works with Terraform and CDK, so infrastructure code is testable.

• JavaScript ecosystem only.
• Service Worker registration adds a setup step and occasional caching confusion.
• Handlers can drift from the real API without contract verification.

• No longer open source: the Community edition is end-of-life, the repo is archived, and running it now requires an account and auth token.
• Using it in CI counts as commercial use, so the free tier does not cover the case most teams want it for.
• Emulation is not identical to AWS; some behaviours and IAM semantics differ.

Front-end teams that want one mocking approach across every kind of test.

AWS-native teams whose tests currently depend on a shared cloud account, and who are willing to pay for a licence now that the free community route has closed.