Software

​Mozilla market

​webob Pylons-framework add-on

​451 test page

Instances

​For DMCA notices

​returns 451 in the UK - NSFW

​Falkvinge.net

Advocacy

UK Open Rights Group: ​451 Unavailable

Media

​The Atlantic

​The Guardian

​Digital Trends

​Techdirt

​CNN

​Motherboard by Vice

​undernews.fr

​Quartz by The Atlantic

​WebMonkey

​The Register

​Forbes

​PublicKey1.jp