How JWT Decoding Works and When Developers Use It
Decode JWT tokens without verification. When to use a JWT decoder for debugging auth and inspecting claims.
How it works
A JWT has three base64url-encoded parts separated by dots: header, payload, and signature. The decoder only decodes the header and payload (it does not verify the signature). It shows the algorithm and token type from the header, and all claims from the payload in pretty-printed JSON. If the payload contains an exp claim, it also shows the expiry as a human-readable date.
When developers use it
Developers use a JWT decoder when debugging authentication flows, checking what claims are inside a token, verifying expiry times, or troubleshooting OAuth or OpenID Connect. It is for inspection only—never use it to trust a token; verification must be done server-side with the correct secret or public key.