Scalar

Scalar is an open-source web app and server that provides tools for building and hosting interactive API documentation. It functions as both a documentation generator and an API client, allowing developers to render OpenAPI and Swagger specifications into a readable format.

The software is available as a web application, a server-side integration, and a desktop application for Windows, MacOS, and Linux. It can be deployed as a single HTML file or integrated directly into various backend frameworks to serve as the default API reference UI.

Key features

• Renders OpenAPI and Swagger documents into interactive references
• Built-in API testing tool for executing requests
• Automatic code example generation for multiple languages and frameworks
• Offline-first API client with environment variables and dynamic parameters
• Watch mode for syncing with server frameworks
• Support for custom themes, layouts, and styling
• Integration with frameworks such as Elysia, Hono, and FastAPI
• OpenAPI parser and converter for Markdown or HTML output

The ecosystem includes a variety of specialized tools, such as a mock server for simulating APIs from OpenAPI documents, a CLI for automation, and an online OpenAPI editor. It is designed for developers who need to maintain technical documentation that stays in sync with their code. The architecture supports a plugin system to extend functionality and offers a universal configuration object for customization.

Scalar is a modern, developer-centric suite for the entire API lifecycle, from specification and testing to final documentation hosting.