Ad blocker

Updated 2026-11-02

Definition

An ad blocker is a browser extension or built-in feature that stops ads and many trackers from loading. It usually works from shared lists of domains and file patterns. Many analytics scripts are on those lists, so a blocker can stop them along with the ads.

When a script is blocked, that visitor is invisible. No pageview, no source and no event gets recorded.

Example

This example uses made-up numbers. Your developer tools site has an audience that often uses blockers. Your server logs show about 10,000 human visitors in a month, but your analytics shows 7,000. So about 30% of visits are missing.

Now think about attribution. Your Stripe account shows 100 payments in that time, and 30 of those buyers had blockers on. Those 30 payments have no visit trail, so they fall into unattributed revenue. At $200 each, that's $6,000 with no channel behind it.

The effect isn't even across audiences. Technical audiences tend to block more than general consumers, so your loss may be far higher or lower than this example.

What helps

Serving your script from your own domain means blockers that work from a domain list are less likely to stop it. That's often called first-party tracking or a proxy. It reduces the loss but won't remove it, since some blockers match by file name or behavior.

Recording money on the server side also helps. Payments stay complete even when browser data doesn't.

How Headstream measures it

The standard Headstream snippet loads from an outside host, so a blocker can stop it. The dashboard has a First-party tracking section under Project settings. It gives you a rewrite for Next.js or Vercel and a snippet that loads from /_hs/t.js on your own domain.

Stripe payments reach Headstream directly, so a blocker can't remove a sale from the ledger, only the visit behind it. See install the script.