Scalar

Scalar is an open-source (MIT) API platform built natively on the OpenAPI standard. Its core is a self-hostable API Reference renderer that turns any OpenAPI or AsyncAPI document into an interactive reference with a built-in request-testing console, multi-language code samples, and modern theming — a drop-in replacement for dated Swagger UI with roughly 14,000 GitHub stars and growing fast.

Around the renderer Scalar ships an offline-first open-source API client (desktop and web), a CLI, an OpenAPI parser, a mock server, and native SDK generation (TypeScript, Python, C#, Java, PHP, Go) from the same document, plus hosted docs sites with guides in Markdown/MDX and MCP servers so AI clients can search your docs or call your API with delegated auth. The open-source components are free and self-hostable; the hosted Scalar Docs platform starts around $150/month. By design it is OpenAPI-first, so teams not already maintaining an OpenAPI document face an adoption step before the tooling pays off.

Drop the @scalar/api-reference package or CDN script into any page with your openapi.json, or sign up for the hosted Scalar Docs platform. CLI available via npm.