OAuth2 Debugger
Debug OAuth2 flows step by step — authorize URLs, code exchange, token inspection. Fix redirect_uri_mismatch in minutes — local tooling, free, no signup.
How to Use the OAuth2 Debugger
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Frequently Asked Questions
redirect_uri_mismatch — why?
Registered redirect must match character-for-character: scheme, host, port, path, and trailing slash. Localhost ports (3000 vs 8080) cause most dev failures.
How do I inspect tokens?
This tool does not decode tokens — it renders the authorize URL, token-exchange body, and sample response shape for a client ID and redirect URI. Decode access/ID tokens elsewhere, and never paste production secrets.
PKCE vs secret?
Public clients (SPA/mobile) use PKCE code_verifier; confidential servers use client_secret. Mixing them fails at the token endpoint by design.
Are my tokens uploaded?
No — debugging runs locally in your browser. Tokens never leave your device — still, use test credentials only.
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Last updated October 2026