What is a JWT Token?
JWT (JSON Web Token) is a compact, URL-safe token format for securely transmitting information between parties. It consists of three parts: header, payload, and signature, separated by dots (e.g., `xxxxx.yyyyy.zzzzz`). To read a JWT token, you need to decode these components individually.
How to Manually Decode a JWT Token
1. **Split the Token**: Break the token into header, payload, and signature sections.
2. **Decode Base64**: Use a Base64 decoder to convert the header and payload from encoded strings to JSON.
3. **Verify Signature** (optional): Validate the signature using the token’s secret key to ensure data integrity.
Example: For token `header.payload.signature`, decode `payload` to see claims like `iss` (issuer) or `exp` (expiration).
Tools to Read JWT Tokens
Use online tools like [jwt.io](https://jwt.io/) or programming libraries to simplify decoding:
- **Online Decoders**: Paste your token to instantly view decoded header and payload.
- **Programming Libraries**: Use Python’s `PyJWT`, JavaScript’s `jsonwebtoken`, or other language-specific packages for programmatic access.
Security Tips When Reading JWT Tokens
- Never trust tokens with expired (`exp`) or invalid signatures.
- Avoid exposing sensitive data in token payloads.
- Always validate tokens on your backend using the correct secret key.
- Use HTTPS to protect tokens during transmission.