OpenAPI Validator

Validate OpenAPI / Swagger 2.0 and 3.0 specifications (JSON or YAML).

Local ProcessingLocal

Note: This tool performs syntactic YAML/JSON validation and basic structure checks. Strict semantic OpenAPI 3.x validation would require external servers.

Paste your OpenAPI spec (JSON or YAML)

Waiting for OpenAPI input...

Why verify your OpenAPI and Swagger specifications offline?

Validate an OpenAPI file here when you want a quick structural check before it goes into documentation, code generation, or a review workflow. It is useful for catching broken JSON, YAML indentation problems, and missing top-level sections before the spec causes issues elsewhere.

Keep internal API specs in your browser

This tool is designed to parse the specification in the browser rather than sending it to a remote validation service. That can be helpful when you are reviewing internal API descriptions, draft specs, or partner-facing files that are not ready to leave your environment.

What this tool does

When an API spec is malformed, the failure usually shows up later in CI, docs generation or client SDK generation. This validator gives you a fast first pass directly in the browser so you can fix obvious structural problems earlier.

Parses both JSON and YAML OpenAPI documents.
Flags basic structural issues such as missing version, info or paths fields.
Provides a lightweight local check before you move on to stricter tooling in CI.

How to use it

1
Paste your OpenAPI or Swagger document into the editor.
2
Let the tool detect whether the content is JSON or YAML.
3
Review the validation panel for syntax or structural errors.
4
Fix the spec locally before sending it to generators, documentation pipelines or repository checks.

Example

A draft spec has routes defined but is missing an info.version, so the validator surfaces the error before code generation fails.

openapi: 3.0.0
info:
  title: Billing API
paths:
  /invoices:
    get:
      summary: List invoices

Validation error: info.version is required.

Use cases

Checking a spec copied from a pull request before merging.
Validating YAML after refactoring route names or shared schemas.
Running a quick first-pass review before stricter CI validation or client generation.

Common mistakes

Expecting full semantic validation

This page focuses on syntax and core structure. You still need stricter linters or CI checks for deeper OpenAPI correctness.

Mixing JSON and YAML syntax

Indentation issues, tabs and malformed quotes often make a YAML document fail before the OpenAPI checks even start.

Forgetting required top-level objects

A useful spec needs more than endpoints. Missing version metadata or info fields breaks many downstream tools.

FAQ

Does this replace Spectral or CI validation?

No. It is a fast local check for immediate feedback, not a full policy engine or contract governance solution.

Can I validate YAML and JSON?

Yes. The tool attempts JSON first and then YAML, which covers the most common OpenAPI authoring formats.

What version fields are supported?

It checks for either the legacy swagger field or the modern openapi field, which covers Swagger 2.0 and OpenAPI 3.x entry points.

Will this upload my API definition?

No. Parsing and checks happen in the browser so draft internal specs do not have to leave your device.

Why is local validation useful if CI already exists?

Local checks shorten the feedback loop and reduce noisy commits, especially when you are iterating on draft specs quickly.

Privacy and security

Specs are parsed locally in the browser.
No internal routes or API descriptions are uploaded for validation.
That is particularly useful for private or pre-release API contracts.

Related tools

Related tools for the next step in the same workflow:

JSON Formatter & Validator YAML Formatter & Validator Diff Checker

Next step

Validate the draft spec locally, then clean up related JSON, YAML, or diff workflows without switching tools.