Fast browser tools for API security testing and debugging.

These tools are designed for quick checks and educational use. They are easy to share, easy to link in articles, and useful enough to become recurring traffic drivers for apisecurity.online.

High intent

JWT Decoder Online

Paste a token and decode header and payload claims in the browser. Great for debugging API authentication and checking expiration, issuer, or audience data.

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High intent

API Header Checker

Analyze response headers to spot missing security controls, risky CORS defaults, cache issues, and stack fingerprinting.

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Developer utility

Rate Limit Tester

Send a short burst of requests from the browser to see whether an endpoint returns 429s or exposes rate limit behavior.

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