FastOS Tools
FastOS Tools

JWT Decoder

Decode and verify JWT tokens online. View JWT header, payload, and signature information.

JWT Token

Introduction

The JWT Decoder tool lets you inspect JSON Web Tokens by decoding their header, payload, and signature parts. It is ideal for debugging authentication bugs, checking claims, and understanding token structure.

When to use this tool

Use this tool whenever you work with JWT-based authentication: verifying token contents, debugging expired or invalid tokens, or learning how JWTs are structured.

How to use

1

Paste your JWT

Copy a full JWT (three dot-separated sections) from your application or API client and paste it into the input field.

2

Decode the token

The tool automatically decodes the header and payload from Base64URL, showing you the JSON content in a readable format.

3

Inspect claims and metadata

Review fields such as issuer, subject, audience, and expiration to verify that the token matches your expectations.

4

Use the decoded data for debugging

Compare decoded values with your server-side configuration when troubleshooting authentication or authorization issues.

Examples

Checking why a user is unauthorized

Decode the user's token to confirm whether required roles or permissions are present in the payload.

Verifying token expiry

Quickly check the exp claim to see whether a token has expired or is close to expiry.

FAQ

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