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OpenAPIFree · Runs in browser

OpenAPI Validator

Validate OpenAPI 2.0, 3.0, and 3.1 documents with clear errors and warnings.

Quick answer

OpenAPI Validator on space4.dev is a free online openapi tool. Validate OpenAPI 2.0, 3.0, and 3.1 documents with clear errors and warnings. It runs entirely in your browser — no signup, no install, and your data is not uploaded to our servers.

Price
Free
Signup
Not required
Processing
100% in your browser
Data uploaded
No
Best for
openapi validator, swagger validator, validate openapi

Features

  • Validate OpenAPI 2.0 / 3.0 / 3.1
  • Detect invalid JSON or YAML
  • Catch missing info, title, version, paths
  • Flag broken $ref and duplicate operationId
  • Warnings for missing descriptions and bodies
  • Copy a full validation report

Frequently asked questions about OpenAPI Validator

Quick answers for privacy, pricing, and how this free online tool works.

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Guide

OpenAPI Validator — complete guide

Why validate OpenAPI documents?

Invalid OpenAPI breaks code generators, API gateways, and documentation portals. A validator catches missing info.title/version, empty paths, duplicate operationIds, broken $ref pointers, and weak response definitions before CI fails.

The OpenAPI Validator on space4.dev checks OpenAPI 2.0, 3.0, and 3.1 locally and returns errors, warnings, and suggestions you can copy into a review checklist.

How to validate OpenAPI / Swagger

Steps:

  • Paste or upload your spec (JSON or YAML).
  • Read the live validation panel for errors vs warnings.
  • Fix blocking errors first (version field, info, paths, responses).
  • Treat warnings (missing descriptions, empty servers) as quality debt.
  • Copy the report for PR comments or ticket notes.

Minimum quality checklist

Every operation should have responses; mutating methods usually need a requestBody; schemas should resolve; operationIds should be unique. Meeting these basics makes your API tooling ecosystem far more reliable.