Listblock

How it works

A phone book that skips the junk.

Listblock works at the DNS level. That's why one setting can cover every device in the house.

DNS, in one paragraph

Every time a device opens a website or an app loads an advert, it first asks a DNS server: "Where do I find this name?" DNS is the internet's phone book. Listblock is a phone book with the entries for known ad, tracker and dodgy-site names left out. If a name isn't in the book, the request goes nowhere, so the ad never loads. Everything else is looked up as normal.

How a lookup travels Your device asks Listblock. Listblock checks its blocklists and passes allowed names to our own Unbound resolver, which finds the website. Blocked names get no answer. If Unbound is unavailable, lookups briefly go to Quad9 or Cloudflare. Your device "Where is example.com?" Listblock checks the blocklists Our Unbound resolver private, in London The website loads as normal Ad or tracker? No answer. Nothing loads. Only if Unbound is unavailable: Quad9 or Cloudflare, briefly How a lookup travels Your device asks Listblock. Listblock checks its blocklists and passes allowed names to our own Unbound resolver, which finds the website. Blocked names get no answer. If Unbound is unavailable, lookups briefly go to Quad9 or Cloudflare. Your device "Where is example.com?" Listblock checks the blocklists Our Unbound resolver private, in London The website loads as normal Ad or tracker? No answer. Only if Unbound is unavailable: Quad9 or Cloudflare, briefly

If our resolver is ever unavailable

If our resolver is ever unavailable, lookups briefly fall back to Quad9 or Cloudflare so your internet keeps working. While that's happening, Listblock's blocklists still apply, but the lookups themselves are answered by one of those two providers instead of by us.

Why our own resolver?

Many DNS services pass your lookups on to a big public resolver. We run our own Unbound resolver on our London server, with DNSSEC validation, so the lookups for the sites you visit stay with us. Logs are kept for 24 hours and then deleted. The privacy policy has the full detail.

What it can't do

Blocking at DNS level is powerful, but it has limits. We'd rather you knew them now.

  • It doesn't block YouTube's in-video ads. Those arrive from the same servers as the video itself, so there's no separate name to block.
  • It can't block ads served from the same domain as the content. If a site puts its ads on its own address, DNS can't tell them apart from the page.
  • It won't block every ad or tracker. Blocklists are good, not perfect. New ad names appear all the time.
  • It isn't a VPN. It doesn't hide your IP address from the sites you visit.

If a site you need stops working, you can add it to your allow-list. See the FAQ.

Set it up