5xx Server error
HTTP 501 Not Implemented
The server doesn’t support the functionality needed to fulfill the request, typically a request method it doesn’t recognize for any resource. 405 is the answer when the method is known but not allowed for one URL.
Defined in RFC 9110, section 15.6.2(opens in a new tab)
//_01 Uptime checks
Is 501 up or down for a monitor?
Uptimecheck HTTP monitor
Default settings
Down. It is outside the default 200–399 range, so a monitor reports an outage once a second check confirms it. If 501 is the answer you expect from that URL, add it to the monitor’s expected status codes.
Is it down? checker
Free, at /is-it-down/
Down. A 5xx means the server, or something in front of it, failed to answer.
//_02 Causes and fixes
Why you see 501 and what to do
Typical causes
- An unusual request method sent to a simple server or proxy.
If you run the site
- Check which methods your clients send, and whether a proxy in front rejects them.
If you’re a visitor
- Nothing to do in a browser.
Know the moment your site stops answering as it should
An Uptimecheck monitor requests your page as often as every minute, checks the status code against the ones you expect, confirms a failure with a second check and then alerts you.
14-day free trial · No credit card required
Questions
What does HTTP 501 mean?
The server doesn’t support the functionality needed to fulfill the request, typically a request method it doesn’t recognize for any resource. 405 is the answer when the method is known but not allowed for one URL.
Does an uptime monitor count 501 as down?
Down. It is outside the default 200–399 range, so a monitor reports an outage once a second check confirms it. If 501 is the answer you expect from that URL, add it to the monitor’s expected status codes.
Downtime is obsolete.
Set up your first monitor in under a minute, or look around the live demo first.
14-day free trial · No credit card required