HTTP 423 Locked vs 521 Web Server Is Down
HTTP 423 (Locked) is a 4xx Client Error response, while 521 (Web Server Is Down) is a 5xx Server Error response. 423 indicates that the resource is locked and cannot be modified (WebDAV). In contrast, 521 means that cloudflare-specific. The origin server refused the connection.
Description
The resource is locked and cannot be modified (WebDAV).
When You See It
When trying to edit a file that another user has locked in WebDAV.
How to Fix
Wait for the lock to be released, or request the lock owner to unlock it.
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
423 is a 4xx Client Error response, while 521 is a 5xx Server Error response.
HTTP 423: The resource is locked and cannot be modified (WebDAV).
HTTP 521: Cloudflare-specific. The origin server refused the connection.
You encounter 423 when when trying to edit a file that another user has locked in WebDAV.
You encounter 521 when when Cloudflare can't establish a TCP connection to the origin server.
When to Use Which
For 423 (Locked): Wait for the lock to be released, or request the lock owner to unlock it. For 521 (Web Server Is Down): Check that the origin server is running and the firewall allows Cloudflare IPs.