Because 1.0.0.1 was never used as a placeholder the way 1.1.1.1 was, it tends to work on networks where 1.1.1.1 is hijacked or blocked. Some people configure it as their primary for that reason.
Notable IP addresses / 1.0.0.1
1.0.0.1
Cloudflare DNS (secondary)
Secondary address for Cloudflare's 1.1.1.1 resolver. Same servers, same privacy policy, fewer legacy-traffic problems than 1.1.1.1.
Related addresses
Frequently asked questions
Is 1.0.0.1 the same as 1.1.1.1?
Yes — the same resolver service announced from the same anycast network.