Free Developer Tool
OpenAPI / Swagger Validator
Validate OpenAPI 2.0 (Swagger) and 3.x specifications. Find broken
$ref
references, missing descriptions, and documentation coverage gaps.
100% Browser-Based
Checks structure, references, and documentation coverage
Spec Overview
Endpoints
| Method | Path | Desc | Ex | Resp |
|---|
Validation Findings
No issues found!
Your specification passed all validation checks.
How to Use
1. Paste or Upload
Paste your OpenAPI JSON or YAML directly into the editor, or click Upload File to load a .json / .yaml file. Format is auto-detected.
2. Validate
Click Validate Specification. The tool checks structural errors, broken $ref references, missing fields, and documentation coverage.
3. Fix & Repeat
Review Errors (must fix), Warnings (should fix), and Info items (nice to fix). Edit and re-validate until clean.
OpenAPI Specification Basics
OpenAPI 3.x vs Swagger 2.0
OpenAPI 3.0/3.1 replaced Swagger 2.0 with richer features: multiple servers,
request body objects, reusable components, and JSON Schema alignment.
Both formats use $ref
to avoid repetition, but 3.x refs live under #/components/schemas/
while 2.0 uses #/definitions/.
$ref References
The $ref keyword lets you reference reusable objects by JSON Pointer.
A broken reference ($ref: '#/components/schemas/Missing')
causes SDK generators and validators to fail silently or with confusing errors.
This tool resolves all internal refs and flags missing targets.
Documentation Coverage
Well-documented APIs include a description and
operationId on every endpoint, error response
codes (4xx / 5xx), and request/response examples. Gaps are surfaced as warnings
so you can prioritise what to fill in first.
100% Client-Side
Parsing and validation run entirely in your browser. Your API specification — which may contain internal paths, security schemes, or proprietary models — is never uploaded to any server.
Validation Checks Reference
| Severity | Check | Why it matters |
|---|---|---|
| Error | Invalid JSON/YAML syntax | Spec cannot be parsed at all |
| Error | Missing version / info / paths fields | Required by every OpenAPI version |
| Error | Broken $ref target | SDK generators and tooling will fail |
| Warning | Endpoint missing description / operationId | Generated clients have no meaningful names |
| Warning | Only 200 response defined | Error handling undocumented |
| Warning | Unused schema definition | Dead code; may indicate copy-paste error |
| Info | Deprecated endpoints | Awareness of sunset timeline |
| Info | Missing contact / license info | Important for public APIs |
Common Use Cases
CI/CD Gate
Paste the spec generated by your build into this tool to catch broken refs or missing required fields before merging a pull request or publishing docs.
SDK Generation Prep
Broken $ref values cause OpenAPI generators to crash.
Validate first so tools like openapi-generator or Speakeasy run cleanly.
Documentation Audit
Use the coverage indicators to quickly see which endpoints are missing descriptions, examples, or error codes — then work through warnings systematically to improve developer experience.
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