OpenAPI / Swagger Editor

Parse, validate, and preview OpenAPI 3.x or Swagger 2.0 documents

Spec Input

2 spaces

Preview

Parsed spec will appear here

Formatted JSON

Formatted output will appear here

About this tool

This tool parses an OpenAPI (3.x) or Swagger (2.0) document supplied as JSON or YAML, validates that it declares an API version and the required info/paths blocks, and renders a browsable preview: the API title and version, declared servers, every operation (method + path + summary), and a count of reusable schemas. The parsed document is re-emitted as formatted JSON. Use it to sanity-check a spec or explore an API without external tooling. Parsing is client-side; nothing is uploaded.

Examples & Use Cases

Minimal OpenAPI 3.1

openapi: 3.1.0
info:
  title: Pet Store API
  version: 1.0.0
paths:
  /pets:
    get:
      summary: List all pets
    post:
      summary: Create a pet

The smallest valid OpenAPI 3.x document — version, info, and a single path with two operations.

Legacy Swagger 2.0

swagger: "2.0"
info:
  title: Legacy API
  version: 0.9.0
host: api.example.com
basePath: /v1
paths:
  /users:
    get:
      summary: List users

Older Swagger 2.0 specs are detected and parsed the same way.

    Examples

    Parse and preview an OpenAPI 3.1 document

    Input
    {"openapi":"3.1.0","info":{"title":"Pet API","version":"1.0.0"},"servers":[{"url":"https://api.example.com"}],"paths":{"/pets":{"get":{"summary":"List pets"}}}}
    Output
    Title: Pet API
Servers: https://api.example.com
Endpoints: GET /pets (1)
Schemas: 0

    After parsing, the preview shows the API title, the server URL, a count of endpoints with their methods, and the total number of schema definitions.

    Detect a Swagger 2.0 document

    Input
    {"swagger":"2.0","info":{"title":"Legacy API","version":"1.0"},"basePath":"/api","paths":{"/users":{"get":{}}}}
    Output
    Detected: Swagger 2.0
Title: Legacy API
Endpoints: GET /users (1)
Schemas: 0

    The tool detects the swagger: "2.0" key and renders a Swagger 2.0 preview. Note that server/basePath handling differs between the two versions.

    About this tool

    OpenAPI & Swagger Editor parses, validates and previews OpenAPI 3.x and Swagger 2.0 specification documents in JSON or YAML. It uses js-yaml to parse the YAML branch, then renders a summary card showing the API title, server list, method-colour-coded endpoint list, and schema count.

    You can also re-emit the parsed document as pretty-printed JSON (or YAML), so you can paste messy input and get clean, reformatted output to paste back into your editor. A clear error banner shows the specific parse error with a line number when the input is invalid.

    All processing — parsing, validation, preview rendering, and re-emission — happens entirely in your browser. Your API specification never leaves your device.

    How to use

    1. Paste or load an OpenAPI spec

      Paste your OpenAPI 3.x or Swagger 2.0 spec in JSON or YAML, or click Load sample to try a built-in example.

    2. Review the preview card

      The preview shows the API title, server URLs, endpoint count (with HTTP methods colour-coded), and the number of schema definitions.

    3. Re-emit formatted output

      Click Format JSON or Format YAML to serialize the parsed document back out in clean, indented form.

    4. Handle errors

      If the spec is invalid, an error banner appears with the specific message and line number so you can fix the source and try again.

    Use cases

    Validating a spec before committing

    Paste your OpenAPI YAML and confirm it parses without errors before pushing it to the repository, catching syntax mistakes early.

    Quick API documentation review

    Share a spec by pasting it into the editor and pointing a reviewer at the URL — the preview card shows the surface area at a glance.

    Re-formatting a messy YAML spec

    Paste hand-edited or machine-generated YAML that has inconsistent indentation, then re-emit the formatted JSON version to restore clean structure.

    Common mistakes

    Mistake:Mixing OpenAPI and Swagger versions in one document.

    Fix:Use exactly one of openapi: 3.x.x (OpenAPI 3.x) or swagger: 2.0 (Swagger 2.0). The tool detects which is present; having both causes a parse error.

    Mistake:Forgetting that YAML keys with colons need quoting.

    Fix:Values containing : followed by space must be quoted in YAML (e.g. "application/json"), otherwise the parser splits them at the colon and produces an invalid structure.

    Frequently asked questions

    Related guides

    OpenAPI 3.x vs Swagger 2.0: What Changed and How to Validate a Spec

    How the API-description format evolved from Swagger 2.0 to OpenAPI 3.x, the practical differences that break importers, and how to sanity-check a spec before shipping it.

    References & standards

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