Bring your contracts
Paste YAML or JSON, drop in your files, or load the example. Set a baseline and a candidate.
PORTFOLIO PROJECTAPI evolution, without the guesswork.
Catch breaking API changes before they ship.
Compare OpenAPI specifications. Understand what changed, what breaks, and what needs a closer look. Before your consumers find out.
No account required. Bring two specs. Get a clear diff.
4 CHANGES DETECTED
2 breaking1 non-breaking1 review
GET /users
Response property type changedUser.id changed from integer to string. Existing clients may fail to deserialize the response.
response · 200 · application/jsonid:
- type: integer
id:
+ type: string
Built for your API contractOpenAPI 3.0 / 3.1YAML / JSONBrowser / CLI / CI
A clear answer in three steps.
Less time reading diffs. More confidence in the next release.
Compare the meaning
Find changes to endpoints, parameters, schemas, and responses — not formatting or key order.
Ship with context
Inspect every finding, share a report, and bring the same checks into your pull requests.
Signal, not noise.
Semantic by design
Understand response types, required fields, and endpoint changes in the context of your OpenAPI contract.
Review-ready findings
Every change comes with a reason and a precise contract location, classified conservatively.
From browser to build
Start with an interactive comparison. Export JSON or Markdown, then automate checks with the CLI.
03 / PRIVACY FIRSTYour contracts.
Your contracts.
Your control.
API specifications can describe sensitive systems. OASFuse compares inputs in memory and intentionally keeps no comparison history.
Read the security principles →Stateless by intention
Comparison inputs are not written to application storage.
No account in the way
The workflow starts with specifications, not sign-up.
Inspectable, not a black box
Rules are deterministic, documented, and shared with the CLI.
Make the next change a deliberate one.
Start with the example, or compare the API you're shipping today.
Start Comparing