OAuth Redirect Hell: A Developer's Debugging Guide

If you've ever implemented OAuth in an app, you've probably spent an evening staring at a redirect error wondering what went wrong. OAuth redirects are deceptively tricky — a single mismatched character can break the entire flow. Here's every redirect problem I've encountered (and fixed) over the years. Problem 1: Mismatched Redirect URIs Symptom: redirect_uri_mismatch error from the provider, usually right after the user authorizes. Cause: The redirect URI in your authorization request doesn't exactly match what's registered in the provider's developer console. And I mean exactly — trailing slashes matter. # Registered in Google Console: https://myapp.com/auth/callback # What your app sends: https://myapp.com/auth/callback/ ← trailing slash = FAIL Fix: Copy-paste the URI from your provider console directly into your code. Don't type it from memory. // Keep redirect URIs in a config, not scattered across your codebase const OAUTH_CONFIG = { redirectUri: process.env.OAUTH_REDIRECT_URI |