JWT Authentication Debugger
When your API rejects a token, the first step is to see what's actually inside it. Our decoder helps you spot missing information or structural errors in seconds.
When to use this solution:
Use this when your application's API calls are failing with authentication errors despite the user being logged in.
Common Use Cases
1Step-by-Step Guide
Capture the problematic token
Get the token string from your application's logs or browser developer tools.
Paste and decode
Paste it into the JWT Decoder to instantly see the raw JSON data.
Check the Header
Ensure the 'alg' (algorithm) matches what your backend expects (e.g., RS256 or HS256).
Verify Payload fields
Confirm that all required fields like 'sub' (subject) or 'aud' (audience) are present and correct.
Ready to get started?
Use our free tool to solve this problem in seconds. No installation required.
Debug Token NowFrequently Asked Questions
Does this tool verify signatures?
This tool is for decoding and inspecting payloads. For signature verification, use a dedicated crypto library with your public/private keys.
What causes an 'invalid format' error?
A valid JWT must have three parts separated by dots. Missing a part or having extra characters will cause decoding to fail.