What it means
The code (named after the novel Fahrenheit 451) says the resource is blocked for legal reasons, such as a court order, a takedown request or regional law. Some US sites return it to visitors from the EU because they aren't GDPR-compliant.
Most common causes
- A court order or takedown request.
- A geographic restriction due to local law.
- Sites that block EU visitors because of GDPR.
- Blocking at the ISP or country level.
What you can do as a visitor
- The content is deliberately blocked, either for your location or everywhere.
- Look for another, legitimate source of the same information.
What the site owner or developer should do
- If you block regions, explain why in the response and, ideally, say who requested the block (Link header with rel="blocked-by").
- Don't use 451 for ordinary geo-licensing restrictions with no legal basis; 403 is more appropriate there.
Impact on SEO and Google
Google doesn't index 451 pages in the regions where they are blocked.
Frequently asked questions
Why do some US sites return 451 in the EU?
Because they've decided not to comply with GDPR and block visitors from the EU.
Can I get around a 451?
The block is a legal one. Use a legitimate alternative source.