Free tools for developers

API Designer

Describe an API and get a working OpenAPI 3.1 spec back.

Understand your API

Paste an OpenAPI spec and get a plain-English explanation of what it does.

Spec editor and visualizer

Design, lint, visualize, and preview OpenAPI specs.

cURL to code

Paste a curl command and get it in your language of choice.

JSON to types

Paste JSON and get TypeScript, Python, or Go types.

Instant mock API

Pick a resource and get a live mock endpoint serving realistic JSON.

Editable mock API

Paste JSON, get a live endpoint, and edit its response anytime.

Mock from OpenAPI spec

Paste an OpenAPI or Swagger spec and mock every endpoint at once.

Test data generator

Generate mock CSV or JSON test rows for API testing.

RPS calculator

Enter users and think time and get estimated throughput and sizing.

AI unit test generator

Paste a function and get unit tests in your framework of choice.

Check API health

Get latency and throughput for any API endpoint.

Check site uptime

See if any API, site, or service is down.

Check site speed

Get response time and TTFB for any website.

Webhook payload explainer

Paste a webhook payload and find out what every field actually means.