JWT Structure Guide: Header, Payload, and Signature Decoded
Exactly what lives in each JWT section, how the signature is computed, and what happens when you decode a token manually.
Published:
Tags: security, jwt, developer-tools
JWT Structure: Header, Payload, and Signature Decoded A JWT consists of exactly three sections. Once you understand what each section contains and how it's constructed, you can read any JWT without a library and understand precisely what guarantees the format provides — and what it doesn't. The Encoding: Base64URL Before examining each section, understand the encoding. JWT sections are base64url encoded — a variant of base64 that uses instead of and instead of , and omits padding (). This makes the output safe for use in URLs and HTTP headers without escaping. Standard base64: , , , , (with padding) Base64url: , , , , (no padding) The difference matters when you're decoding manually — you need to swap the characters back before calling . Section 1: The Header The header is a JSON object…
All articles · theproductguy.in