JWT Decoder Tool - JSON Web Token Inspector and Debugger

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Free JWT Decoder and Inspector for JSON Web Tokens. All decoding is performed entirely within your browser - your tokens never leave your device or get sent to any server. Unlike jwt.io, this tool does not transmit your token data anywhere.

  • This tool is provided "AS IS" without any warranties of any kind.
  • The author accepts no responsibility for any security issues arising from handling tokens.
  • This tool only decodes JWTs — it does not verify signatures. Do not use this as a security validation tool.
  • Never paste production tokens with sensitive data into any online tool unless you trust its privacy model.
  • By using this tool, you accept full responsibility for any outcomes.

Privacy: This tool uses client-side JavaScript for all processing. No data is transmitted to servers, no tokens are uploaded online, all processing happens locally in your browser. Once loaded, this tool continues to work even without an internet connection. For more details, please refer to our Web Tools Disclaimer.

HEADER (Algorithm & Token Type)

PAYLOAD (Claims / Data)

SIGNATURE (Hex)

All Claims

Claim Value Type Description

Features:

  • JWT Decoding: Paste any JWT and instantly decode its Header, Payload, and Signature sections.
  • Expiration Check: Automatically checks if the token is expired, valid, or has no expiration set, with time remaining or elapsed.
  • Token Status Panel: Displays algorithm, type, key ID, issuer, subject, audience, and all timestamp claims at a glance.
  • Claims Table: Lists all claims with their values, type (Registered or Custom), and descriptions for standard claims.
  • Auto-Decode on Paste: Automatically decodes the JWT when you paste it into the input field.
  • Signature Display: Shows the signature as a hexadecimal string for inspection.
  • Copy Functions: Copy header, payload, or all decoded sections individually.
  • 100% Client-Side: All processing happens in your browser. Your tokens never leave your device — unlike jwt.io which may transmit token data.
  • Works Offline: Once loaded, the tool works without an internet connection.
  • No External Libraries: Pure vanilla JavaScript with zero dependencies.

How to Use:

  1. Paste JWT: Copy a JWT token and paste it into the input field. The tool will auto-decode on paste.
  2. Decode: Click "Decode JWT" to manually decode the token.
  3. Review Header: Check the algorithm (e.g., HS256, RS256) and token type in the blue HEADER section.
  4. Review Payload: Inspect all claims including issuer, subject, audience, and expiration in the green PAYLOAD section.
  5. Check Expiration: The Token Status panel shows whether the token is VALID or EXPIRED with the time difference.
  6. Inspect Claims: The Claims Table lists every claim with its type (Registered/Custom) and description.
  7. Copy Results: Use "Copy Header", "Copy Payload", or "Copy All Decoded" buttons to copy results to your clipboard.

Important Notes:

  • This tool only decodes JWTs — it does not verify digital signatures. Do not rely on this tool for security validation.
  • JWT decoding does not require a secret key. The header and payload are simply Base64URL-encoded, not encrypted.
  • Never include real production tokens with sensitive claims in screenshots or shared documents.
  • The expiration check uses your local system clock. Ensure your system time is accurate for correct results.
  • Supports all standard JWT algorithms (HS256, RS256, ES256, etc.) for display, but does not perform cryptographic verification.
  • Handles both standard and URL-safe Base64 encoding in JWT segments.

References:
Tech Blog with curated related content
Web Tools Collection

Written by Hidekazu Konishi