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Yaak vs WebSocket King: catalog facts
Yaak	WebSocket King
Freemium Yaak is MIT licensed and free to build and use. Development is funded by…	Free Free to use in the browser.
Windows, macOS, Linux	Web
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	Nothing to install Focused on WebSocket testing and debugging
A much younger project than Postman, with a smaller community No hosted collaboration features if that is what you actually want	WebSockets only, not a general HTTP client Little public documentation about its features
Downloadable app	Web application
Open source	Closed source
License: MIT	License not stated
No account needed	Not stated if an account is needed
Works offline	Not stated if it works offline
Official website Full listing and sources Checked September 21, 2026	Official website Full listing and sources Checked September 24, 2026

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