# Is your DNS filter blocking ads?

> Find out whether your network's DNS filter (Pi-hole, AdGuard DNS, NextDNS) or a browser extension stops ads and trackers. Free, in your browser.

Free in-browser tool (no upload): https://www.mauriziofonte.it/tools/dns-ad-blocking-test

The test tries to reach ad and tracker domains and looks at where they stop: on the network, in a browser extension, or somewhere the page cannot pin down. When the blocking happens on the network, it also shows which DNS resolver goes out to the Internet.

## How to use the DNS ad blocking test

1. **Open the page on the device you want to check** - A DNS filter only protects the devices that use it: run the test from the phone, PC or TV you care about, on your home network.
2. **Let the test run** - It starts by itself after loading; press Analyze to run it again. It takes a few seconds.
3. **Read where the blocking happens** - Network, browser extension, both or neither. When both are active, the result says so instead of guessing.
4. **Separate the two layers** - Turn extensions off and run it again: whatever stays blocked is stopped by the network.

## Why a DNS filter sometimes does nothing

Pi-hole and other DNS filters only work when the device sends its DNS questions to them. When the test says nothing blocks, it is usually one of these.

**The device uses another DNS.** The router may still hand out your provider's DNS, sometimes only over IPv6, and the device uses that instead of the filter.

**The browser has secure DNS set to a provider.** With DNS over HTTPS the browser asks the chosen provider directly, and the network filter never sees the requests.

**A VPN is on.** A VPN usually brings its own DNS.

**The answer is cached.** A domain resolved before you turned the filter on stays valid until its answer expires: restart the browser, flush the system DNS cache and run the test again.

## Glossary

- **Ad blocker**: A tool that stops ads and trackers from loading while you browse. It can be a browser extension or a blocker that works across your whole home network.
- **Tracker**: Small pieces of code that follow what you do online (which pages you visit, what you click) to build a profile and show you targeted ads. A good blocker stops them along with the ads.
- **uBlock Origin**: The most recommended ad-blocking extension: free, lightweight and effective, for Chrome, Firefox and Edge. Be careful not to confuse it with the many clones that have similar names.
- **Pi-hole**: A small "filter" you set up at home (often on a Raspberry Pi) that blocks ads for every device on the network, including TVs and phones. It can't hide the empty boxes on pages.
- **NextDNS / AdGuard DNS**: Services that block ads and trackers at the network level, without installing an extension. A few settings and they protect every device. Like Pi-hole, they don't hide empty slots.
- **Acceptable Ads**: A feature, on by default in Adblock Plus, that lets some ads deemed "non-intrusive" through. It's the most common reason for a only-partial score. It can be turned off in the extension settings.
- **Empty slot (ad box)**: When an ad is blocked but its empty box is left behind on the page. Browser extensions can hide it; network blockers can't.
- **Brave**: A browser with ad and tracker blocking built in (called Brave Shields). No extension needed: it protects against both connections and empty slots.

## Questions about the DNS ad blocking test

### I run Pi-hole but the test says nothing blocks. Why?

This device most likely does not ask Pi-hole. Check which DNS server it uses in the network settings, whether the router hands out a different IPv6 DNS, whether the browser has secure DNS set to a provider, and whether a VPN is on. Then run the test again.

### How do I tell DNS blocking from extension blocking?

Run the test with extensions turned off. Whatever stays blocked is stopped by the network; whatever gets through was stopped by the extension.

### Does the test see my Pi-hole's address?

No. Pi-hole and AdGuard Home forward requests to an outside DNS, and that is what the test sees. AdGuard DNS and NextDNS are recognized when the exit resolver falls in address ranges known to be theirs.

### Does the test load real ads?

It tries to download the real scripts of ad and tracking services, without showing any ad. If nothing in your setup blocks them, those requests really reach those services, as on any other website.

### Why does the test query dns.google?

It is the reference that tells whether a test domain still exists. The request leaves from your browser, so Google sees your IP address as any site would; the only names asked are those of the test domains.

### Does it work on a phone?

Yes, from the phone's browser on your home Wi-Fi. On mobile data the phone does not go through your Pi-hole, unless a VPN or a private DNS setting points at your filter.

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Tool by Maurizio Fonte, senior backend engineer. All tools: https://www.mauriziofonte.it/tools/