Question 1

What is a JWT and how is it structured?

Accepted Answer

JWT (JSON Web Token) is a secure way to transmit information as a JSON object. It consists of three Base64-encoded parts separated by dots: Header (algorithm info), Payload (claims/data), and Signature (verification).

Question 2

Is it safe to decode JWTs client-side?

Accepted Answer

Yes, decoding is safe - JWTs are designed to be readable by clients. However, never expose sensitive data in JWT claims since anyone can decode them. The signature verifies authenticity, but payload data is not encrypted.

Question 3

What are JWT claims and how do I read them?

Accepted Answer

Claims are statements about an entity (usually the user). Standard claims include "iss" (issuer), "exp" (expiration), "sub" (subject), and "aud" (audience). Custom claims can contain any JSON data your application needs.

Question 4

How do I verify if a JWT is valid?

Accepted Answer

This tool only decodes JWTs - it doesn't verify signatures. To verify validity, you need the secret key or public key used for signing. Check expiration dates, issuer, and other claims in your application logic.

Question 5

Why might JWT decoding fail?

Accepted Answer

Common reasons include: malformed token structure (not 3 parts), invalid Base64 encoding, corrupted characters, or tokens that aren't actually JWTs. Ensure you're pasting the complete token including all dots.

JWT Decoder

Примеры JWT токенов

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