You’re happily coding along, integrating a third-party login like Google or GitHub, when boom — an unfamiliar error pops up in your browser. It says something like:
“Error: redirect_uri_mismatch”
Panic sets in for a moment. But relax — this error is common, and fixing it is actually pretty simple. Let’s take a fun, no-jargon journey through what this error is, why it happens, and most importantly, how to squash it fast.
What is a Redirect URI?
First things first. To understand the problem, you need to know what a redirect URI is.
When a user logs in using a third-party service, like Google, a specific URI (Uniform Resource Identifier) is where the service will send the user back after completing authentication. This URI tells the service, “Hey! After login, send them back to this address!”
This address could look something like:
https://myapp.com/auth/callback
It’s a way to securely get users back to your app after proving who they are.
So What’s a Redirect URI Mismatch?
It happens when the URI registered with the third-party service doesn’t match the URI you’re using in your app. Think of it like telling your friend to pick you up from 123 Main Street, but then you actually wait for them at 321 Main Street — you both end up confused.
Services like Google are very picky about this. If you register a redirect URI with HTTPS and include a trailing slash, and your actual request uses HTTP or omits the slash, boom, you’ve got a mismatch.
Common Causes of a Redirect URI Mismatch
Here’s a quick list of common troublemakers:
- HTTP vs. HTTPS: One uses HTTPS but the other doesn’t.
- Trailing Slash: Your registered URI ends with a slash, but your app doesn’t (or vice versa).
- Typo: A small spelling error — easy to miss, but it’ll break everything.
- Wrong Subdomain: One says app.example.com and the other says www.example.com.
- Environment Differences: Using localhost for development but having production redirect differences.
Basically, everything has to match exactly. No close-enough. No “eh, it’ll probably work.”
How to Fix a Redirect URI Mismatch Fast
Here’s your go-to fix-it checklist. Follow these simple steps:
- Find the registered redirect URI.
Go to your third-party provider’s developer console (like Google Cloud Console or GitHub Developer Settings). Look for where you registered your redirect URI. - Double-check your app’s redirect URI.
Find the code or configuration inside your app where you set the redirect URI. Make sure this EXACTLY matches what you registered. - Copy & Paste Carefully.
Copy your registered URI and paste it into your app’s settings. Don’t type it manually — prevent typos! - Check for those tricky little things.
Look out for:- Extra slashes
- Capitalization
- Different subdomains
- Port numbers (like :3000 vs no port)
- Update and Save.
After correcting the URI on either the developer console or in your code (wherever it was wrong), be sure to save the changes.
Example with Google Sign-In
Let’s say you’re using Google Sign-In. In your Google Developer Console, you set:
https://mycoolapp.com/auth/google/callback
But in your app’s config you had:
https://mycoolapp.com/auth/google
This won’t work. Google says, “This is not what you told me before!”
To fix it, you simply make sure both sides match:
https://mycoolapp.com/auth/google/callback
Copy that into your app’s code or environment variable and boom — error gone.
Handling Redirects in Different Environments
This gets tricky when you have different setups like:
- Development: http://localhost:3000/auth/callback
- Production: https://mycoolapp.com/auth/callback
In that case, register both URIs with your provider. Most services let you enter multiple URIs — do it! That way, your app works both locally and online.
What If You’re Still Stuck?
If things still aren’t working, try these advanced debugging tips:
- Log the redirect URI before sending it. Print it to console or log it. Are you sending what you think you are?
- Check for environmental variables. Maybe you’re using a variable like REDIRECT_URI that’s misconfigured.
- Use an online URL matcher tool. Some dev tools or debuggers can spot differences between URLs character by character.
- Contact support. If it’s a third-party service like Google, they have forums and support teams too.
Bonus Tip: Always Use HTTPS in Production
Most services (definitely Google) require HTTPS for production apps. If you’re still using HTTP, that might also cause the mismatch. Get an SSL certificate. It’s free with services like Let’s Encrypt!
Prevent It in the First Place
Don’t want to see this error again? Then:
- Keep redirect URIs in one config file or environment variable.
- Use a shared constants file across frontend and backend.
- Always test redirects in all environments after making changes.
Having a system helps avoid mismatching URIs and the headache that follows.
In Conclusion
Redirect URI mismatch errors are annoying, but they’re actually pretty easy to fix.
Just remember:
- Exact match = success
- Almost match = error
Now go ahead and fix that pesky login error. With your new knowledge, you’ll solve this in minutes — maybe even seconds!
Happy coding and may your redirects always match perfectly 🔗!