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Swagger / OpenAPI Editor

Write or paste an OpenAPI 3 or Swagger 2 definition and see it checked as you type: syntax errors with line numbers, structural problems, and a browsable list of every endpoint. Convert between YAML and JSON in one click.

  • Free to use
  • No sign-up
  • Runs in your browser
View

Type or paste a definition on the left, or press Load example. The preview and the checks update as you type.

This editor parses and checks your document and shows the API as a list. It does not send requests (a “Try it out” button would need to contact your API from your browser), and its checks are practical structural checks, not a full validation against the OpenAPI schema.

Good to know

This is a lightweight editor. It checks the structure of your definition and previews it, but it is not a complete OpenAPI validator and it does not send requests to your API. Use your usual tooling for full validation before publishing.

How to use the Swagger / OpenAPI Editor

  1. Step 1: Paste your OpenAPI or Swagger definition into the editor, or press Load example to start from a small sample.

  2. Step 2: Watch for a syntax error message. It gives the line and column of the first problem in YAML or JSON.

  3. Step 3: Open the API preview to browse the title, servers and every operation grouped by tag. Click an operation to see its parameters and responses.

  4. Step 4: Open the Problems tab to read errors and warnings from the structural checks, each with the place in the document it refers to.

  5. Step 5: Press Convert to JSON or Convert to YAML, then Copy or Download the result.

Features and benefits

  • YAML and JSON

    Both formats are read automatically, and you can convert from one to the other without retyping.

  • Errors with line numbers

    Syntax mistakes, such as bad indentation or a missing comma, are reported with their line and column.

  • Structural checks

    Missing versions, unresolved references, duplicate operation ids, undeclared path parameters and responses without descriptions are found for you.

  • Endpoint preview

    Operations are listed by tag with their method, path, parameters and responses, so you can see the API the way a reader would.

  • OpenAPI 3.x and Swagger 2.0

    Both generations of the specification are understood.

What the checks cover

After the document parses, the editor looks for the mistakes that most often break real definitions. It requires an openapi or swagger version, an info title and version, and a paths object. It checks that every path starts with a slash, that each operation has a responses section, that response codes are valid and have descriptions, and that operation ids are unique.

It also checks that every placeholder in a path, such as {petId}, has a matching path parameter marked required, and that every local reference, such as #/components/schemas/Pet, points to something that exists. Missing summaries, operation ids and servers are reported as warnings because they do not make the document invalid.

What it does not do

The checks are practical but not exhaustive. They do not validate every keyword of every schema against the full OpenAPI specification, they do not follow references to other files or addresses, and they do not render example payloads. There is also no Try it out button: sending a request from a web page to your API would require the API to allow it, and would involve contacting a server, which this site does not do with your content.

Working with large definitions

The editor accepts up to one million characters. The preview updates a moment after you stop typing, so large files stay responsive. Your definition is never uploaded, and nothing is saved: copy or download your work before you close the page.

Example use cases

  • Drafting a new API

    Sketch endpoints in YAML and see them take shape before writing any code.

  • Fixing a broken definition

    Find the exact line of a syntax error or the missing reference that makes other tools reject your file.

  • Reviewing someone else's API

    Scan the endpoint list and response codes without reading hundreds of lines of YAML.

  • Converting formats

    Turn a YAML definition into JSON, or the reverse, for a tool that only accepts one.

Frequently asked questions

Does it support both Swagger 2.0 and OpenAPI 3?

Yes. Swagger 2.0 and OpenAPI 3.0 and 3.1 definitions are understood, in YAML or JSON.

Is this the official Swagger Editor?

No. It is a lighter, independent tool that runs entirely in your browser. For the complete official toolchain use the tools from the OpenAPI community.

Can I test my API from here?

No. The editor does not send requests, which keeps your definition private and avoids cross-site request problems.

Why does it say a reference is unresolved?

A $ref such as #/components/schemas/Pet points to a place that does not exist in the document. Check the spelling and the path.

Is my API definition uploaded?

No. It is parsed and checked in your browser and is never sent or stored.

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Last updated 11 November 2026.