What it means
The server cannot provide the resource for legal reasons, such as a court order or government censorship. The number nods to Fahrenheit 451.
Common causes
- Content blocked in certain countries
- DMCA or court-ordered takedown
- Sanctions or GDPR geoblocking
How to fix it
As a client or visitor
The content is unavailable in your region or was removed; the body may explain who required it.
As the site or API owner
Explain the legal demand and, if possible, link to the authority with a Link rel="blocked-by" header.
Example response
HTTP/1.1
HTTP/1.1 451 Unavailable For Legal Reasons
Date: Tue, 07 Oct 2025 09:30:00 GMT
Server: nginx
Link: <https://authority.example.org>; rel="blocked-by"
Content-Length: 0Specification
FAQ
› Why 451?
A reference to Ray Bradbury's novel Fahrenheit 451 about censorship.
› 451 vs 403?
451 makes clear that a legal demand, not a permission rule, blocks access.