501 Not Implemented — Causes & Fix
HTTP 501 (Not Implemented) means the server does not support the functionality required to fulfil the request — usually an HTTP method it doesn't recognise or support.
- Applies to
- Any website or web server (HTTP standard)
- Time to fix
- 15 minutes – 2 hours
What it means
Causes include using a method the server doesn't implement, or requesting a feature the server lacks. This is a server-side (5xx) error defined in RFC 9110 (HTTP Semantics) — the request was valid, so the fix is on the server/origin side, not the visitor's.
Symptoms
- "501 Not Implemented"
- A particular method/feature fails while normal pages work
How to fix it
- 1
Use a supported method
1. As a developer/client: use an HTTP method/feature the server supports.
- 2
Enable the feature (operator)
1. Implement or enable the required functionality on the server, or use a server that supports it.
Frequently asked questions
501 vs 405?
405 means the resource exists but the method isn't allowed for it; 501 means the server doesn't implement that method/feature at all.
Last updated July 20, 2026
Guidance only — always consult a qualified professional or the official service manual before carrying out repairs.