Paste
Use two representative payloads. Nothing is uploaded.
LOCAL-FIRST WEBHOOK CONTRACT CHECK
Will this webhook change break your consumer?
Paste old and new JSON. Get breaking-risk candidates and a ready-to-run regression test—processed only in your browser.
No sign-upNo payload uploadNo storage
Scan two payloads free
FREE SCAN
Compare two payloads
Your payload stays here. Comparison and test generation run in this browser. Do not paste secrets.
RESULT
Consumer-risk candidates
These are candidates inferred from two samples—not proof of the provider's complete contract. Confirm against provider documentation and your consumer code.
Regression fixture and test
NOT JUST A JSON DIFF
From changed syntax to consumer impact
Review
See removed paths, type shifts, shape changes, and uncertainty.
Test
Copy a fixture-based regression test into your suite.
PRICING HYPOTHESIS
Scan once free. Monitor continuously when it matters.
Free
¥0
- One-off browser scan
- Risk explanations
- Jest/Vitest fixture test
- No account or history
Monitor
¥2,980 / month
- Local CLI / GitHub Actions
- Up to 5 monitored contracts
- Schema-diff history
- CI checks and notifications
- Multiple test frameworks
FAQ
What this scanner does—and does not do
Is my payload uploaded?
No. The scanner does not send your JSON, field names, values, or generated test to a server. Anonymous product events contain only action names.
Does a High result prove a breaking change?
No. It is a candidate based on two samples. Whether it breaks depends on your consumer code and the provider's documented contract.
Why not use a generic JSON diff?
A generic diff shows syntax. This tool classifies likely consumer impact and creates a regression test you can adapt.