OAuth2 Token Debugger - Decode Tokens & Parse Auth URLs

What Is an OAuth2 Token Debugger?

An OAuth2 Token Debugger is a developer tool for inspecting OAuth2 and OpenID Connect (OIDC) authentication flows. It can decode JWT-format access tokens and ID tokens to reveal their header and payload claims, and it can parse OAuth2 authorization URLs to extract parameters like client_id, redirect_uri, scope, response_type, state, and PKCE challenges. This makes it easier to troubleshoot authentication issues, verify token contents, and understand authorization request parameters during development.

How to Use the OAuth2 Token Debugger

1. Select the 'Decode Token' tab to inspect a JWT token, or 'Parse Auth URL' to analyze an authorization URL.
2. For token decoding, paste your access_token or id_token. The tool decodes the JWT header and payload and displays them as formatted JSON.
3. For URL parsing, paste a full OAuth2 authorization URL (e.g., from your browser address bar during a login flow).
4. The URL parser extracts and labels all query parameters, highlighting known OAuth2 parameters like client_id, scope, and PKCE fields.
5. Review the extracted information to verify your OAuth2 configuration is correct.

Common Use Cases

• Debugging Login Flows — When an OAuth2 login flow fails, paste the authorization URL to verify that client_id, redirect_uri, and scope parameters are set correctly.
• Inspecting ID Tokens — After an OIDC authentication, decode the id_token to verify the user's identity claims such as email, name, and audience.
• PKCE Verification — Check that your authorization request includes the correct code_challenge and code_challenge_method parameters for PKCE flows.
• Token Scope Validation — Decode access tokens to verify that the granted scopes match what your application requested and needs.