The HTTP 501 Not Implemented server error response code indicates that the request method is not supported by the server and cannot be handled. The only methods that servers are required to support (and therefore that must not return this code) are GET and HEAD.
Note that a 501 error is not something you can fix, but requires a fix by the web server you are trying to access.
A 501 response is cacheable by default.
501 Not Implemented
| Specification | Title |
|---|---|
| RFC 7231, section 6.6.2: 501 Not Implemented | Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content |
| Feature | Chrome | Edge | Firefox | Internet Explorer | Opera | Safari | Servo |
|---|---|---|---|---|---|---|---|
| Basic Support | (Yes) | (Yes) | (Yes) | (Yes) | (Yes) | (Yes) | (Yes) |
| Feature | Android | Chrome for Android | Edge Mobile | Firefox for Android | IE Mobile | Opera Mobile | Safari Mobile |
|---|---|---|---|---|---|---|---|
| Basic Support | (Yes) | (Yes) | (Yes) | (Yes) | (Yes) | (Yes) | (Yes) |
© 2005–2017 Mozilla Developer Network and individual contributors.
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-US/docs/Web/HTTP/Status/501