OpenAPI and Swagger Spec Validator
Check the basic structure of an OpenAPI 3.x document (openapi, info, paths), browse the endpoints grouped by path, and catch common issues such as missing responses or duplicate operationIds. JSON input only - YAML is not parsed.
FreeOnline Tool
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How to Use
- Paste the JSON content of your OpenAPI (Swagger) document into the text box.
- Press "Validate and parse". The tool checks the openapi version field, the required info.title and info.version fields, and that paths exists and is not empty.
- Once it passes, the "Endpoints" list below groups every operation by path, showing the HTTP method, summary/description and operationId.
- The tool also raises warnings that do not block parsing: missing responses definitions, missing summary/description and duplicate operationIds.
- Press "Load sample OpenAPI document" for a complete document that deliberately triggers warnings, so you can see each rule in action.
Features
- Basic structural validation: the openapi version field, the required info.title and info.version fields, and a non-empty paths object.
- Visual endpoint listing grouped by path, including HTTP method, summary/description and operationId.
- Warnings for common problems: missing responses definitions, missing summary/description and repeated operationIds.
- Only JSON OpenAPI documents are parsed - there is no YAML parser. Input that looks like YAML is called out explicitly rather than silently reported as valid; convert it with the site's YAML to JSON tool first.
- Swagger 2.0 documents (identified by the swagger field) are recognized and explicitly reported as unsupported, so the results are never misleading.
- Parsing is entirely local; the document is never uploaded.
Use Cases
Self-checking an API document before submission
Run a quick check for missing base fields and endpoints without responses before committing or merging an OpenAPI document.
Skimming a third-party API
Paste an open platform's OpenAPI JSON and browse every available endpoint as a list without setting up a Swagger UI.
Checking operationId naming
Find duplicate operationIds in a large API document before a code generator such as openapi-generator fails or emits confused output.
Reviewing documentation completeness
Spot endpoints missing a summary or description as part of a technical documentation review.
FAQ
Does it accept YAML OpenAPI documents?
Not currently - there is no YAML parser, only JSON. If you paste YAML the tool detects it and states plainly that only JSON is supported rather than pretending validation passed. Convert it with the site's YAML to JSON tool first.
Is Swagger 2.0 supported?
Not yet. The tool looks for the swagger field and reports that only OpenAPI 3.x is supported, instead of judging a Swagger 2.0 document by OpenAPI 3.x rules.
Does it resolve $ref and check schema types in depth?
No. It only performs basic structural validation (the openapi, info and paths fields) plus common-issue warnings (responses, summary, operationId). It does not resolve $ref or deeply validate schemas - use a dedicated OpenAPI validator for full spec compliance.
Is my document uploaded?
No. All parsing and validation happen locally in your browser.