Listblock

How it works

A phone book that skips the junk.

Listblock works at the DNS level. That's why setting it on your home router 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

We look things up ourselves.

Many DNS services pass your lookups on to a big public resolver, such as Google, Cloudflare or Quad9. We don't. Each of our two London servers runs Unbound, a recursive resolver: it starts at the internet's root servers and looks the name up itself.

That way, the site's own DNS servers see our server's address, not yours. Unbound also checks DNSSEC, so it can tell if an answer has been tampered with. It remembers names it has already looked up, and refreshes popular ones before they expire, so common sites stay fast.

We keep those lookup logs for 24 hours, then delete them. The privacy policy has the full detail.

If our resolver is ever unavailable

Quad9 and Cloudflare are only used as a backup if our own resolver is down. If that happens, lookups briefly fall back to one of them so your internet keeps working. Listblock's blocklists still apply, but the lookups themselves are answered by that provider instead of by us.

More than one server

We run two servers in London. They share the load, and your settings are kept on both. If one is down, your devices use the other.

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