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OpenAPI Generator

Turn a plain list of endpoints into a valid OpenAPI 3.1 document with paths, components and schemas.

Build an OpenAPI 3.1 document

Paths: 0 · Operations: 0 · Schemas: 0
Add one endpoint per line, then indented detail lines.
Detail lines: question mark name colon type for query parameters, star name colon type for path parameters, double exclamation mark for a JSON body, and a status code colon schema name for responses.

How to use the OpenAPI Generator

  1. Paste one endpoint per line, such as GET /pets, then indented parameter, body and response lines.
  2. Set the API title, version, server URL and choose YAML or JSON output.
  3. Press Generate document, then copy the finished OpenAPI 3.1 file into your repository.

Features

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Frequently Asked Questions

Common questions about the free online openapi generator.

Paste your endpoints one per line, add the parameter, body and response lines beneath each, then press Generate document.
The generator emits an OpenAPI 3.1.0 document with an info block, servers, paths and a components section holding every schema.
Yes. Choose JSON in the output format list and the document is rendered as pretty printed JSON with two space indentation.
Start a detail line with two exclamation marks and paste a JSON sample. The object is turned into a named schema under components.
A question mark marks a query parameter and a star marks a path parameter, which is also written into the required list.
A status code followed by a colon and a schema name adds that response. Use none for codes that return no content.
No. Everything is parsed and rendered inside your browser, so your endpoint list never leaves the page.
The output follows the OpenAPI 3.1 layout, with summary, operationId, parameters, requestBody, responses and schemas in place.
Press Load sample to drop in a small pet store document, then edit the lines to match your own service.
Yes. The tool is completely free, needs no account and has no limits on how many documents you build.

Last updated: October 10, 2026