Down Checker / Error codes

Website error codes explained

Each page says what the code means, which side failed, the usual causes and what to check first, with the Down Checker to test the site as you read.

• 500The application crashed while building the page.
• 502A proxy, load balancer or CDN in front of the site asked the application for the page and got an invalid answer, or none: the connection was refused or reset, or the response was malformed..
• 503The server is up but is refusing to handle requests for the moment: maintenance mode, too many requests, or no healthy backend behind a load balancer..
• 504A proxy, load balancer or CDN waited for the application to answer and gave up after its timeout.
• Cloudflare 520Cloudflare connected to your origin server, but the answer was empty, malformed or not something Cloudflare understands..
• Cloudflare 521Cloudflare reached your origin's address, but the web server refused the connection: nothing is listening, or a firewall blocks Cloudflare..
• Cloudflare 522Cloudflare tried to open a TCP connection to your origin and got no answer in time.
• Cloudflare 523Cloudflare cannot find a route to your origin.
• Cloudflare 524Cloudflare connected to your origin, but the application took longer than Cloudflare's 100-second limit (on most plans) to send a response..
• Cloudflare 525In Full or Full (strict) mode, Cloudflare connects to your origin over HTTPS, and the TLS handshake with the origin failed..
• Cloudflare 526In Full (strict) mode Cloudflare checks the origin's certificate, and it failed: expired, self-signed, or not valid for this hostname..
• Cloudflare 530Cloudflare could not resolve or reach the origin; the page shows a second, 1xxx error that names the reason (1016: origin DNS error is the most common)..
• 403The server understood the request and refused it.
• 429The server or a firewall is rate-limiting: this client sent more requests than allowed in a time window..
• 502 vs 503 vs 504The three gateway errors side by side.