308 Permanent Redirect

The 308 Permanent Redirect is an HTTP status code that indicates the requested resource has been permanently moved to a new location, and the client should use the new URL for all future requests. This status code is similar to the 301 Moved Permanently status code, but with one key difference: the 308 Permanent Redirect requires the client to maintain the same HTTP method when following the redirect.

Usage and Implications

The 308 Permanent Redirect status code is used when a resource has been permanently moved to a new location, and you want the client to continue using the same HTTP method for future requests. This is particularly important when dealing with non-idempotent methods like POST, where changing the method to GET could have unintended consequences.

When a client receives a 308 Permanent Redirect response, it should:

1. Update any bookmarks or references to the old URL.
2. Use the new URL for all future requests, maintaining the same HTTP method.
3. Include any request headers that were sent with the original request, unless the new URL is on a different domain.

Example Request and Response

Consider a scenario where a client sends a POST request to create a new resource, but the server has permanently moved the endpoint to a new location.

Request

POST /old-endpoint HTTP/1.1
Host: example.com
Content-Type: application/json
Content-Length: 42

{
  "title": "A new resource",
  "body": "Some content"
}

Response

HTTP/1.1 308 Permanent Redirect
Location: https://example.com/new-endpoint
Content-Length: 0

In this example, the server responds with a 308 Permanent Redirect status code and a Location header containing the new URL. The client should now send the same POST request to the new URL.

Comparison with Other Redirect Status Codes

The 308 Permanent Redirect status code is not the only redirect status code available in HTTP. Here’s a brief comparison with other common redirect status codes:

• 301 Moved Permanently: Indicates that the resource has been permanently moved to a new location, but the client is allowed to change the HTTP method when following the redirect (e.g., from POST to GET).
• 302 Found and 307 Temporary Redirect: Both indicate that the resource has been temporarily moved to a new location, and the client should continue using the original URL for future requests. The key difference is that 302 Found allows the client to change the HTTP method when following the redirect, while 307 Temporary Redirect requires the client to maintain the same method.

Best Practices

When implementing the 308 Permanent Redirect status code, consider the following best practices:

• Use the 308 Permanent Redirect status code when you want to enforce that the client maintains the same HTTP method when following the redirect.
• Always include the Location header in the response, providing the new URL for the client to use.
• Ensure that the new URL is fully qualified, including the scheme (e.g., https://) and domain.
• Test your implementation to verify that clients correctly follow the redirect and maintain the same HTTP method.

Summary

The 308 Permanent Redirect is an HTTP status code that indicates a permanent redirection to a new URL while maintaining the same HTTP method. It is particularly useful when dealing with non-idempotent methods like POST. When implementing this status code, ensure that you provide the new URL in the Location header and follow best practices to ensure a smooth redirection process for clients.