← Blogby Marcell Almeida

How to audit JWT tokens for security issues

Paste a JWT — see security warnings for alg, expiry, and weak configurations.

JWT misconfigurations cause real breaches — alg:none attacks, expired tokens accepted, missing audience checks. The JWT Security Checker decodes pasted tokens and flags common vulnerabilities.

Try it — paste JWT token

Open full tool →

How it works

  1. Paste JWT — access or ID token from your app.
  2. Decode — header and payload shown as JSON.
  3. Security audit — warnings for alg, exp, and claim issues.

What it checks

Flags alg: none, missing exp, expired tokens, weak algorithms, and suspicious claim combinations. Does not verify signatures — use your auth server for that.

Decode only

For payload inspection without security audit, use the JWT Decoder.

The How to audit JWT tokens for security issues is free, runs locally, and never sends your data to a server. More developer tools at maratool.com.