Back to Home

OpenAPI / Swagger Validator

Validate OpenAPI 3.x and Swagger 2.0 specifications with detailed error reporting. Use this free online tool directly in your browser.

Processed locally — your data never leaves your browser
Loading tool...

What is OpenAPI / Swagger Validator?

OpenAPI (formerly Swagger) is the industry standard specification format for describing REST APIs. An OpenAPI document describes every endpoint, request parameter, response schema, and authentication requirement for an API in a machine-readable YAML or JSON file. Tools like Swagger UI, Redoc, and API client generators all consume this format. This validator checks your specification against the OpenAPI 3.x and Swagger 2.0 rules — detecting missing required fields, malformed paths, operations without response definitions, and common structural mistakes. It reports errors (blocking issues), warnings (best-practice violations), and suggestions (improvements for client generation and documentation quality). Everything runs in the browser, so you can safely validate internal API specs without uploading them to an external service.

How to use

  1. 1

    Paste or enter your data in the OpenAPI / Swagger Validator input area.

  2. 2

    Run the conversion, generation, or validation action.

  3. 3

    Copy or download the result for your project workflow.

Common Use Cases

  • 1

    Validate an OpenAPI spec before publishing it to a developer portal or API gateway

  • 2

    Check for missing operationId fields before generating client SDKs with tools like OpenAPI Generator

  • 3

    Detect missing response definitions that would cause documentation gaps or client generation failures

  • 4

    Verify that every path starts with a slash and has at least one defined operation

  • 5

    Audit a third-party API specification before integrating it to catch malformed schemas early

Try an Example

Pet Store API

Load this sample to see a passing OpenAPI 3.0 validation.

Example Input

openapi: "3.0.3"
info:
  title: Pet Store API
  version: "1.0.0"
paths:
  /pets:
    get:
      summary: List pets
      responses:
        "200":
          description: OK

Frequently Asked Questions

What is OpenAPI / Swagger Validator?

OpenAPI / Swagger Validator is a free browser-based utility on Bite Size Tools. Validate OpenAPI 3.x and Swagger 2.0 specifications with detailed error reporting.

Is OpenAPI / Swagger Validator safe to use with sensitive data?

Yes. Tool processing runs in your browser, so your input is not sent to a server by default in this app.

Can I use OpenAPI / Swagger Validator for production work?

Yes. You can use the output directly in development and production workflows after validating it with your project requirements.

Related Tools

YAML ↔ JSON Converter

Convert YAML and JSON in both directions with validation and download support

JSON Formatter & Validator

Paste JSON and format it with proper indentation, validate structure and highlight errors

HAR File Analyzer

Analyze HTTP Archive (HAR) files to inspect requests, timings, status codes, and performance