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scalar/scalar

Open-source OpenAPI/Swagger toolkit with an interactive API reference, an offline-first API client, and integrations for many web frameworks.

Open-source alternative to:PostmanSwagger UI

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16,304
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958
Open issues
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Last commit
3 hours ago

What is it?

Scalar is a TypeScript project that turns OpenAPI and Swagger documents into interactive API reference pages. Developers can add it to a single HTML file from a CDN or to an existing server through integrations for frameworks such as Express, FastAPI, Hono, NestJS, Next.js and Spring Boot.

The same project includes an API client for sending requests, with support for environment variables and dynamic parameters. It is available in the browser or as a desktop app for Windows, macOS and Linux, and a watch mode can sync it with a running server framework.

The repository is a monorepo that also contains packages for parsing OpenAPI documents, converting them to Markdown or HTML, upgrading specification versions, and a CLI. Hosted services such as a document registry, documentation hosting and a mock server are offered separately by the Scalar company.

Key features

  • 01Renders OpenAPI and Swagger documents as interactive API reference pages.
  • 02Includes an API client for testing requests, with environment variables and dynamic parameters.
  • 03Generates code examples for many languages and frameworks.
  • 04Offers integrations for dozens of server frameworks and documentation tools.
  • 05Provides an offline-first desktop app for Windows, macOS and Linux, plus a browser version.

Use cases

  • Adding a browsable documentation page to an existing REST API built with FastAPI, Express or Spring Boot.
  • Testing endpoints from an OpenAPI description without installing a separate tool like Postman.
  • Generating client code samples for an API's consumers in several programming languages.

Quick start

  1. 1

    Create a single HTML file that loads the API Reference ESM build from the CDN (no build step needed)

  2. 2

    Open the HTML file in a browser to view the interactive API reference

Things to know

  • The HTML quick start loads the library and a CORS proxy from Scalar's hosted CDN and proxy servers, so you depend on those services unless you self-host.

Topics

#openapi#swagger#api-documentation#api-client#rest-api#typescript#http-client#api#docs#openapi3

FAQ

What is scalar?
Open-source OpenAPI/Swagger toolkit with an interactive API reference, an offline-first API client, and integrations for many web frameworks. Scalar is a TypeScript project that turns OpenAPI and Swagger documents into interactive API reference pages. Developers can add it to a single HTML file from a CDN or to an existing server through integrations for frameworks such as Express, FastAPI, Hono, NestJS, Next.js and Spring Boot.
Is scalar free to use? What license does it have?
scalar is open source under the MIT license. Check the license terms before using it in commercial products.
Is scalar still maintained?
Actively maintained. The last commit to scalar was on Oct 22, 2026.
What can I use scalar for?
Adding a browsable documentation page to an existing REST API built with FastAPI, Express or Spring Boot. Testing endpoints from an OpenAPI description without installing a separate tool like Postman. Generating client code samples for an API's consumers in several programming languages.
How do I install scalar?
Create a single HTML file that loads the API Reference ESM build from the CDN (no build step needed) Open the HTML file in a browser to view the interactive API reference
Where can I get scalar?
The source code and installation instructions are on GitHub: https://github.com/scalar/scalar

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