The Critical World of HTTP Redirects
URL redirects are fundamental to web architecture, enabling site migrations, content reorganization, and URL structure changes. However, not all redirects are created equal. The HTTP specification defines four primary redirect status codes—301, 302, 307, and 308—each with specific semantics and use cases. Choosing the wrong redirect can harm SEO rankings, break application functionality, or create security vulnerabilities.
The Fundamental Distinction: Permanent vs. Temporary
The primary distinction between these redirect codes is whether they indicate a permanent or temporary move:
Permanent Redirects: 301 and 308
Permanent redirects tell clients that the original URL is no longer the correct address and all future requests should use the new location. Search engines interpret permanent redirects as a signal to transfer ranking signals from the old URL to the new one.
301 Moved Permanently is the traditional permanent redirect, widely supported across all browsers and servers. When a resource has permanently moved to a new URL, 301 tells clients that the original URL is no longer available and should be replaced.
308 Permanent Redirect is the newer permanent redirect status code, introduced in RFC 7538 in April 2015. It serves the same fundamental purpose as 301 but with an important difference in how it handles HTTP methods.
Temporary Redirects: 302 and 307
Temporary redirects indicate that the resource has moved, but the original location may become available again in the future. Clients should continue using the original URL for future requests.
302 Found is the traditional temporary redirect. It tells the client that the original location may become available again, and the client should continue to use the original URL for subsequent requests.
307 Temporary Redirect is the modern temporary redirect equivalent, similar to 302 but with stricter method preservation requirements.
The Critical Difference: HTTP Method Handling
The most significant technical distinction between these redirect codes lies in how they handle the HTTP request method during redirection.
Method-Changing Redirects: 301 and 302
Both 301 and 302 allow browsers to change the HTTP method from POST to GET when following the redirect. This behavior, while not originally intended, became established through historical browser implementations and is now codified in modern HTTP specifications.
When a user submits a form via POST to a URL that returns a 301 or 302 redirect, browsers typically convert the request to GET when following the redirect. This makes sense for many scenarios—after processing a form submission, you usually want to redirect to a results page that should be fetched with GET.
However, this method-changing behavior is problematic when you need to preserve the original HTTP method, such as redirecting one API endpoint to another while maintaining POST semantics.
Method-Preserving Redirects: 307 and 308
Both 307 and 308 require the client to use the same HTTP method when following the redirect. If the original request was POST, the redirected request must also be POST. If it was PUT, the redirect must use PUT.
This strict method preservation is crucial for API design and situations where the semantics of the HTTP method must be maintained. For example, when redirecting a RESTful API endpoint that accepts POST requests, using 307 or 308 ensures the client sends a POST request to the new location, not a GET request.
The main difference between 307/308 and 301/302 is that the HTTP method must be retained during the redirection, maintaining the original GET/POST request structure.
SEO Implications and Link Equity
From an SEO perspective, the distinction between permanent and temporary redirects is crucial, but the difference between method-preserving and method-changing variants is less significant.
Link Equity Transfer
Google has stated that it treats 301 the same as 308 and 302 the same as 307 from an SEO perspective. All four redirect types—301, 302, 307, and 308—equally count as a signal to transfer ranking signals from the old URL to the new one, with no dampening effect or loss of link juice.
This means that for standard webpage redirects involving GET requests, the choice between 301 and 308 or between 302 and 307 won't impact your search rankings. The permanent versus temporary distinction is what matters for SEO.
Permanent Redirects for Site Migrations
When permanently moving content, always use a permanent redirect (301 or 308). This signals to search engines that they should:
- Transfer ranking signals to the new URL
- Update their index to show the new URL
- Stop crawling the old URL
Using a temporary redirect (302 or 307) for a permanent move confuses search engines, potentially causing them to continue indexing the old URL and splitting ranking signals between both URLs.
Temporary Redirects for Maintenance and Testing
Use temporary redirects (302 or 307) when:
- Performing site maintenance
- Running A/B tests
- Temporarily moving content that will return to its original location
This tells search engines to keep the original URL in their index and not transfer rankings to the temporary location.
Browser Compatibility Considerations
While all four redirect codes are part of the HTTP standard, browser support varies, particularly for the newer codes.
Universal Support for 301 and 302
The 301 and 302 status codes have been part of HTTP since the beginning and are universally supported across all browsers, including older versions. You can use these codes with confidence that they'll work everywhere.
Limited Support for 308
The 308 status code is relatively new and not supported by all browsers. Notably, Internet Explorer 11 on Windows 7 and 8 doesn't understand 308 status codes. When these browsers encounter a 308, they may not follow the redirect correctly.
For maximum compatibility, the recommendation is to always use 301 redirects, unless you require POST requests to be redirected properly and are certain that all clients understand the 308 response code.
Support for 307
The 307 status code has broader support than 308 and is generally safe to use in modern applications, though some very old browsers may not handle it correctly.
Practical Use Cases and Recommendations
Understanding when to use each redirect code is essential for correct implementation.
Use 301 Moved Permanently When:
- Permanently changing your site's domain
- Restructuring your URL architecture
- Consolidating multiple pages into one
- Moving content to a new permanent location
- Migrating from HTTP to HTTPS
These are all scenarios where you want search engines to transfer rankings and where the old URL will never be used again.
Use 302 Found When:
- Redirecting users during site maintenance
- Creating temporary landing pages for campaigns
- Implementing device-specific redirects (mobile to desktop)
- A/B testing different versions of a page
- Temporarily moving content that will return
Use 302 when the original URL will be restored or when you don't want to affect search engine indexing of the original URL.
Use 307 Temporary Redirect When:
- Temporarily redirecting API endpoints
- Maintaining HTTP method semantics in temporary redirects
- Working with form submissions that need to preserve POST method
- Building applications where method preservation is critical
Use 307 when you need the temporary redirect semantics of 302 but must preserve the HTTP method.
Use 308 Permanent Redirect When:
- Permanently redirecting API endpoints
- Maintaining POST/PUT/DELETE semantics in permanent redirects
- Working with modern client applications that support 308
- Building RESTful services where method preservation is essential
Use 308 when you need permanent redirect semantics with guaranteed method preservation, but ensure all clients support it.
Implementation Best Practices
Regardless of which redirect code you choose, following best practices ensures effective implementation.
Minimize Redirect Chains
Each redirect adds latency and negatively impacts user experience and SEO. Aim for no more than one redirect per URL. When restructuring sites, update internal links to point directly to the final destination rather than relying on redirect chains.
Update Internal Links
After implementing redirects, update internal links to reference the new URL directly. This reduces server load, improves page load times, and provides a better user experience.
Include Retry-After Header for 503
When using 503 Service Unavailable during maintenance, include a Retry-After header specifying when the client should try again. This helps both users and search engines understand the temporary nature of the issue.
Test Redirect Implementation
Always test redirects to ensure:
- They return the correct status code
- The Location header points to the intended destination
- HTTP methods are preserved when using 307/308
- No redirect loops exist
- Performance impact is acceptable
Monitor Redirect Performance
Track redirect metrics including:
- Redirect response times
- Percentage of traffic hitting redirects
- Redirect chain depth
- 4xx/5xx errors from redirect destinations
Common Mistakes to Avoid
Understanding what not to do is as important as knowing best practices.
Using 302 for Permanent Moves
One of the most common and costly mistakes is using 302 for permanent site migrations. This can cause search engines to continue indexing the old URL, splitting ranking signals and harming organic visibility.
Using 301 for Method-Sensitive Redirects
When redirecting API endpoints that receive POST, PUT, or DELETE requests, using 301 or 302 can cause the method to change to GET, breaking the application. Use 307 or 308 to preserve the method.
Creating Redirect Loops
Misconfigured redirects can create loops where URL A redirects to URL B, which redirects back to URL A. This makes the resource inaccessible and wastes server resources. Always test redirect chains thoroughly.
Forgetting to Update Sitemaps
When implementing permanent redirects, update your XML sitemap to include the new URLs and remove the old ones. This helps search engines discover and index the new URLs quickly.
Conclusion
The differences between 301, 302, 307, and 308 redirects are subtle but significant. The key distinctions are:
- 301 vs. 302: Permanent vs. temporary redirect, both allow method changes
- 307 vs. 308: Temporary vs. permanent redirect, both preserve HTTP methods
- 301/302 vs. 307/308: Method-changing vs. method-preserving behavior
For standard web page redirects involving GET requests, use 301 for permanent moves and 302 for temporary ones. For API redirects where HTTP method preservation is critical, use 308 for permanent redirects and 307 for temporary ones, but verify browser support for 308.
Understanding these differences and choosing the appropriate redirect code for each scenario ensures your redirects work correctly for both users and search engines, maintaining SEO rankings while providing reliable application behavior.
