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WebSocket KingYaak
Free

Free to use in the browser.

 Freemium

Yaak is MIT licensed and free to build and use. Development is funded by…

Web Windows, macOS, Linux
  • Nothing to install
  • Focused on WebSocket testing and debugging
  • Requests are stored as files on your machine, so a git repository is the shared collection
  • REST, GraphQL, gRPC, WebSocket and Server-Sent Events in one client
  • WebSockets only, not a general HTTP client
  • Little public documentation about its features
  • A much younger project than Postman, with a smaller community
  • No hosted collaboration features if that is what you actually want
Web application Downloadable app
Closed source Open source
License not stated License: MIT
Not stated if an account is needed No account needed
Not stated if it works offline Works offline

Checked September 24, 2026

Checked September 21, 2026

Catalog facts only. Anything “not stated” is unconfirmed. Check full listings for details.