451 Unavailable For Legal Reasons
4xx client error
Access is denied because of a legal demand, such as a court order or a government block.
451 — a nod to Ray Bradbury's Fahrenheit 451 — was standardised in RFC 7725 so that legal blocks are transparent. Instead of a vague 403 or 404, the server says the content is unavailable because of a legal obligation, and can identify who demanded it with a Link: <…>; rel="blocked-by" header.
| Class | 4xx Client Error |
|---|---|
| Retry? | No — change the request first |
| Cacheable by default | No — only with explicit Cache-Control |
| Response body | Allowed |
| Defined in | RFC 7725 — An HTTP Status Code to Report Legal Obstacles |
Example response
HTTP/1.1 451 Unavailable For Legal Reasons
Content-Type: application/json
Content-Length: 41
{"error":"Unavailable For Legal Reasons"}Common causes
- Court-ordered takedowns, or government blocking in certain countries.
- Sites blocking regions where they can't meet legal requirements — some US news sites returned 451 to EU visitors when GDPR took effect.
How to fix it
- As a visitor, there's usually nothing to fix: the block is deliberate.
- As an operator, explain the block in the body and include the
blocked-byLink header.
Send a 451 from your server
Express
res.status(451).json({ error: "Unavailable For Legal Reasons" });Next.js route handler
return Response.json({ error: "Unavailable For Legal Reasons" }, { status: 451 });Flask
return {"error": "Unavailable For Legal Reasons"}, 451Go net/http
http.Error(w, "Unavailable For Legal Reasons", http.StatusUnavailableForLegalReasons)
nginx
return 451;
Check what a URL returns
Print just the status line from the command line, or check a whole list of URLs at once, with their response headers, in the HTTP Status Checker.
curl -sI https://example.com/your-path | head -n 1
Frequently asked questions
Why the number 451?
It references Fahrenheit 451, Ray Bradbury's novel about book burning — fitting for a status code about censorship.
Related status codes