A 301 redirect is an HTTP status code indicating that a resource has been permanently moved to a new URL. When a server responds with a 301 status, it includes a Location header specifying the new URL. Browsers automatically follow the redirect, and search engines treat the new URL given in the Location header as the one that should be indexed.
The 301 redirect is the most important redirect type for SEO. Google Search Central documentation states that the indexing pipeline uses a permanent redirect as a signal that the redirect target should be canonical, while it doesn't use a temporary redirect as that signal (as of April 2026). That is why 301 is the recommended choice for permanent URL changes such as site migrations, domain changes, and URL structure updates.
In URL shortening, 301 redirects are used when the short URL is intended to be a permanent alias for the destination. Since browsers cache 301 redirects, subsequent visits to the same short URL may bypass the shortening service entirely, which improves speed but reduces the accuracy of click tracking.
The trade-off between 301 and 302 redirects is a key design decision for URL shortening services. A 301 sends the clearest signal about which URL is canonical but is harder to track, while a 302 preserves tracking accuracy and leaves the original URL as the indexed one. Many services default to 301 for branded links and 302 for campaign links.