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JWT Decoder

Developer Tools

Decode header/payload, inspect claims and expiry

Quick Answer

JWT Decoder: Decode header/payload, inspect claims and expiry. Three Base64URL segments: Header.Payload.Signature.

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How to Use

  1. Paste or type content: drop code/text into the JWT Decoder or fill the parameters.
  2. Choose mode/options: switch format, rules or processing as needed.
  3. Live output: results appear instantly — nothing is submitted, data stays in your browser.
  4. One-click copy: copy the output straight into your development environment.

Key Points

  • JWT Decoder is a free online developer tool — open and use, no sign-up.
  • All calculations run locally in your browser; your data never leaves the device.
  • Key capability: Decode header/payload, inspect claims and expiry.
  • Results come with formulas and reference tables so you can verify every number.

Formula & How It Works

JWT structure (JSON Web Token)

Three Base64URL segments: Header.Payload.Signature
Header: alg + typ; Payload: claims (sub/iss/exp/iat/nbf)
Timestamps are Unix seconds; expired when exp < now
Base64URL: +/ → -_, padding = dropped
Decoding ≠ verifying — never put secrets in the payload

Example: {alg: HS256} {sub: 1234} is readable by anyone holding the token.

FAQ

How do I use the JWT Decoder?
Open the page and fill in the input fields — results update automatically. Decode header/payload, inspect claims and expiry.
Are the results accurate?
Yes. Standard formulas and conversion factors are used and verified.
Is it free? Do I need to sign up?
Completely free. No registration, login or download required.
Does it work on mobile?
Yes. The responsive design works on phones, tablets and desktops.
Is my data saved?
No. Everything runs locally in your browser.

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Source & Updates

Based on RFC 4648, ECMA-262 and related specifications. Last updated: 2025-07

Authoritative sources:

Last updated:

Formulas and content on this page are reviewed by the YiJianSuan team. For reference only — official sources prevail.

Cite this page: YiJianSuan. JWT Decoder[EB/OL]. https://www.yijiansuan.com/en/c/dev/jwt

Results provided by this tool are for reference only and do not constitute professional advice.