9/4/2025
The OAuth 2.0 protocol is instrumental in securing modern web and mobile applications. It allows applications to gain authorized access to protected user resources without asking for users’ credentials directly. However, during implementation, many developers encounter a frustrating and recurring error ‘redirect_uri_mismatch’.
Why You Keep Getting ‘redirect_uri_mismatch’ in OAuth 2.0 & What To Do
This error can halt access token requests, impair workflows, and waste significant development time if misunderstood. In this article, we explain exactly why this error occurs, what its causes are, and how to resolve it in various environments.
What is the ‘redirect_uri_mismatch’ Error?
The ‘redirect_uri_mismatch’ error occurs when the OAuth 2.0 authorization server (e.g., Google, Microsoft, or any identity provider) receives a redirect_uri in an authorization request that doesn’t match any of the URIs pre-registered by the application in that server’s dashboard or console.
In OAuth 2.0, redirect_uri is the endpoint to which the authorization server sends responses back to the client application. To prevent security vulnerabilities like open redirects or phishing, this endpoint must be predefined and exact. Any minor discrepancy can trigger a mismatch error and shut down the entire authorization workflow.
Common Causes of the Error
Even though the definition seems straightforward, triggering this error is very easy due to several subtle causes. Let’s break them down:
- Mismatch in Registered and Requested URI: The most frequent cause is that the URI in the API request doesn’t match the one listed in your OAuth client’s configuration.
- Trailing Slashes: A URI with or without a trailing slash (e.g., https://example.com/callback vs. https://example.com/callback/) is considered different. This tiny difference can trigger a mismatch error.
- HTTP vs. HTTPS: Many identity providers are strict about protocols. http:// and https:// are not interchangeable.
- Localhost vs. 127.0.0.1: Though they point to the same place, http://localhost and http://127.0.0.1 are treated as different hosts in URI matching.
- Environmental Differences: Issues may occur during deployment or when switching from development to production environments if each uses a different base URL or callback path. URL Encoding Issues: Improper encoding of special characters like &, ?, or even spaces can create subtle mismatches.
- OAuth Library Quirks: Variability in how different OAuth libraries construct URIs can result in mismatches, particularly when assembling dynamic redirect URIs.
How to Fix The ‘redirect_uri_mismatch’ Error
Fixing the redirect_uri_mismatch error involves a systematic process of verifying and aligning redirect URIs between your code and the identity provider’s configuration settings. Here are the most effective strategies:
- Verify URIs in Your Application Code
- Check the Registered Redirect URIs in OAuth Provider Settings
- Use Environment-Specific Redirect URIs
- Inspect the Actual Request Being Sent
- Avoid Dynamically Constructed Redirect URIs (If Possible)
- Check with the OAuth Provider’s Docs
- Prevent Common Pitfalls