What schema formats does the validator support?

JSON Schema (Draft 7 and Draft 2020-12), OpenAPI 3.0 and 3.1 response schemas, and custom field-level assertions (status code, field presence, value ranges).

How does schema validation catch breaking changes?

When your API returns a field with the wrong type, removes a required field, or changes a value format, the schema validator catches it immediately. Without schema validation, these breaking changes only surface when client applications start failing.

Free Tool

Free API Schema Validator

Paste your API response and schema. Get instant validation showing every field mismatch, type error, and missing required field.

This API response schema validator checks live endpoint output against expected contracts so teams can catch drift before clients fail. It is valuable for APIs with multiple consumers where small field or type changes can create wide production impact. Instead of discovering schema breaks through user-facing incidents, developers can verify response integrity continuously and during release validation. This strengthens API reliability and reduces downstream integration regressions.

What this tool detects

Missing required fields in API responses
Type mismatches against expected schema
Contract drift that breaks dependent clients

Q: Is schema validation only useful in CI?

A: No. CI catches pre-release mismatches, while runtime validation catches production drift, environment issues, and third-party behavior changes.

Optional: paste JSON Schema or OpenAPI response schema. We infer expected field paths from it.

What We Check

1
Enter API endpoint or paste JSON - Enter API endpoint URL, or paste response JSON directly.
2
Upload schema - Upload or paste your expected JSON Schema or OpenAPI spec.
3
API request - API request made and response captured.
4
Field-by-field validation - Response body validated against schema field by field.
5
Type mismatch detection - Type mismatches detected (e.g. string returned where integer expected).
6
Missing field flagging - Missing required fields flagged.
7
Extra field reporting - Extra fields not in schema reported.
8
Full diff report - Full diff report showing passing and failing assertions.

FAQs

What schema formats does the validator support?: JSON Schema (Draft 7 and Draft 2020-12), OpenAPI 3.0 and 3.1 response schemas, and custom field-level assertions (status code, field presence, value ranges).
How does schema validation catch breaking changes?: When your API returns a field with the wrong type, removes a required field, or changes a value format, the schema validator catches it immediately. Without schema validation, these breaking changes only surface when client applications start failing.

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