HTTP 451 Unavailable For Legal Reasons

What does HTTP 451 mean?

Access is denied because of a legal demand. Named after Fahrenheit 451. Used when content is blocked by court order, government censorship or regional legal restrictions; the response should explain the demand and who made it.

4xx Client error: The request has a problem the client can fix: wrong URL, missing credentials, bad data or too many requests.

451 and SEO

The page is not indexed in regions where it returns 451.

Example response

HTTP/1.1 451 Unavailable For Legal Reasons

How to return a 451 response

Node.js (Express)

res.status(451).json({ error: 'Unavailable For Legal Reasons' });

PHP

http_response_code(451);

Python (Flask)

return {'error': 'Unavailable For Legal Reasons'}, 451

Go (net/http)

w.WriteHeader(451)

nginx

return 451;

Related status codes

• 403 Forbidden — The server understood the request but refuses to authorize it.
• 404 Not Found — The server cannot find anything at the requested URL.
• 410 Gone — The resource has been permanently removed and will not return.

Check which status code a URL returns with the HTTP header checker.