301Moved

301Moved, commonly referred to as 301 Moved Permanently, is an HTTP status code in the 3xx family indicating that the resource requested by the client has been permanently moved to a new URL. The new URL is provided in the Location header of the response. Clients are expected to use the new URL in future requests, and user agents often update bookmarks automatically.

As a permanent redirect, 301 responses are typically cached by browsers and intermediate caches, and search engines treat them as a signal to transfer the indexing and ranking signals from the old URL to the new one. This makes 301 redirects a preferred tool for long-term URL changes. However, they can interact with SEO in nuanced ways: if overused or placed in chains, they may slow indexing or dilute signal transfer. The code also implies that the old URL should no longer serve the original content.

Common use cases include moving content to a new URL after a site redesign, changing domain names or protocols (for example, http to https or www to non-www), and canonicalizing URLs to a preferred version. Best practices include ensuring the final destination is stable and relevant, avoiding redirect chains and loops, and updating internal links and sitemaps to point directly to the new URL.

Implementation varies by server. Examples include Apache with a 301 Redirect directive, Nginx with a 301 return or rewrite rule, and application code that sends a 301 status and a Location header, such as in PHP.