OpenAPI validator
Run bounded local structural checks on an OpenAPI 3 JSON document without resolving references.
How it works & useful details
Local-only workspace
This tool converts or inspects pasted text in your browser. It never sends a request, opens a URL, uploads a HAR, or stores your input.
Bounded structural checks
This checker accepts JSON OpenAPI 3.0/3.1 documents and checks the required root, info, path, operation and responses shapes. It does not resolve $ref entries, parse YAML, contact servers, or certify a contract.
About this tool
OpenAPI validator runs structural checks on a pasted OpenAPI 3 document and reports problems with the fields it can verify without leaving your browser. It is a fast first pass before you hand a spec to a full validator in your build pipeline.
The checks are deliberately bounded: references are not resolved, so a specification with external or remote $ref targets is only checked where the document itself provides the information. Every limitation is reported instead of being hidden.
How to use it
- Paste the OpenAPI JSON document.
- Run the validation to see version, info, paths, and component issues.
- Read the reported problems and warnings in the results panel.
- Copy the report into your issue tracker or fix the spec and re-run.
Worked example
{
"openapi": "3.0.3",
"info": { "title": "Notes API", "version": "1.0.0" },
"paths": {
"/notes": { "get": { "responses": { "200": { "description": "OK" } } } }
}
}passes the structural checks: version 3.0.3, title "Notes API", one path with a GET operation. Removing the responses object, or info.version, produces a specific issue instead of a pass.
What is and is not checked
The validator checks the skeleton every OpenAPI 3.0 and 3.1 document needs: an openapi version string, an info object with title and version, and a paths object whose operations each define responses. These are the mistakes that break code generators and documentation tools first.
It does not resolve $ref references, validate schemas in depth, or read YAML. Convert YAML specs with YAML to JSON first. For complete validation before publishing, run a full linter such as Spectral or Redocly in your build. This tool is for a quick, private sanity check of a spec you do not want to upload anywhere.
Frequently asked questions
Does it resolve $ref references?
No. Remote and external references are not fetched or resolved; the validator only checks what is present in the pasted document.
Is this a full OpenAPI schema validator?
It is a bounded structural check for common mistakes. For a complete conformance check, run a dedicated validator in your pipeline.
What is the limit?
Up to 500,000 characters of JSON text.
Does it support Swagger 2.0?
No. Swagger 2.0 uses a different root structure ("swagger": "2.0"). Convert it to OpenAPI 3 with a dedicated converter first.