A token that contains all necessary information and doesn't require server-side storage.
Stateless JWT tokens are self-contained tokens that store user information in their payload, which the server can verify without keeping a session on the server. This improves scalability by reducing server memory usage. For example, a JWT consists of three parts: a header, a payload, and a signature, all base64 encoded.
Additional Notes
How would you explain a Stateless JWT token in an interview?