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JWT decoder guides
Three short reads: why this matters, how to do it, and one specific way to use it.
Why APIs Traded Server-Side Sessions for a Signed Token
A server-side session is simple and instantly revocable, but it needs a lookup every single server can reach on every request. A JWT trades that lookup for a signature - and gives up instant revocation to get it.
Read the guideHow to Check Whether a JWT Has Expired, Without Doing the Epoch Math Yourself
A JWT's exp claim is a raw Unix timestamp - meaningless at a glance. Paste a token and the expiry, not-before, and issued-at claims come back as real dates with a plain valid/expired/not-yet-valid label, no manual conversion required.
Read the guideDebugging a 401 by Reading What Your JWT's Claims Actually Say
A request that worked five minutes ago now returns 401, and the token looks fine at a glance. The fastest way to find out what changed is to decode it and read the claims in order, not guess.
Read the guide