Server error
503 503 Service Unavailable
The server is temporarily unable to handle the request — overloaded, or deliberately in maintenance mode. It is the correct code for planned downtime.
Common causes
- Traffic beyond capacity.
- A maintenance mode flag left switched on.
- An auto-scaling group with no healthy instances.
How to fix it
- During planned maintenance, return 503 with a Retry-After header: search engines come back rather than de-indexing you.
- Never serve a maintenance page with a 200 status — that tells search engines your content is now the maintenance notice.
See what a site actually returns
Run a live check and read the real status code, headers and timings.
Other status codes
200 OK
201 Created
204 No Content
206 Partial Content
301 Moved Permanently
302 Found
303 See Other
304 Not Modified
307 Temporary Redirect
308 Permanent Redirect
400 Bad Request
401 Unauthorized
403 Forbidden
404 Not Found
405 Method Not Allowed
408 Request Timeout
410 Gone
413 Payload Too Large
418 I'm a Teapot
429 Too Many Requests
451 Unavailable For Legal Reasons
500 Internal Server Error
501 Not Implemented
502 Bad Gateway
504 Gateway Timeout
507 Insufficient Storage
508 Loop Detected
521 Web Server Is Down
522 Connection Timed Out
523 Origin Is Unreachable
525 SSL Handshake Failed