HTTP 301 Moved Permanently vs 521 Web Server Is Down
HTTP 301 (Moved Permanently) is a 3xx Redirection response, while 521 (Web Server Is Down) is a 5xx Server Error response. 301 indicates that the resource has been permanently moved to a new URL. All future requests should use the new URL. Search engines will transfer link equity to the new URL. In contrast, 521 means that cloudflare-specific. The origin server refused the connection.
Description
The resource has been permanently moved to a new URL. All future requests should use the new URL. Search engines will transfer link equity to the new URL.
When You See It
After domain migrations, URL restructuring, or when consolidating duplicate URLs.
How to Fix
Update links and bookmarks to the new URL in the Location header. For SEO, this is the preferred redirect for permanent moves.
Description
Cloudflare-specific. The origin server refused the connection.
When You See It
When Cloudflare can't establish a TCP connection to the origin server.
How to Fix
Check that the origin server is running and the firewall allows Cloudflare IPs.
Key Differences
301 is a 3xx Redirection response, while 521 is a 5xx Server Error response.
HTTP 301: The resource has been permanently moved to a new URL. All future requests should use the new URL. Search engines will transfer link equity to the new URL.
HTTP 521: Cloudflare-specific. The origin server refused the connection.
You encounter 301 when after domain migrations, URL restructuring, or when consolidating duplicate URLs.
You encounter 521 when when Cloudflare can't establish a TCP connection to the origin server.
When to Use Which
For 301 (Moved Permanently): Update links and bookmarks to the new URL in the Location header. For SEO, this is the preferred redirect for permanent moves. For 521 (Web Server Is Down): Check that the origin server is running and the firewall allows Cloudflare IPs.