How to detect AdBlock in plain JavaScript with a few lines of code

Using analytics tools to measure the impact is part of every website these days.

But measuring how many of your users block analytics is probably even more important.

And luckily, it’s not that difficult to figure it out.

How it works

In a nutshell - you need to add a fake advertisement div to your website and check if it is visible or not.

In practice:

  1. Add an empty div that’s positioned in the top right corner of your website. That way, it won’t bother users who don’t use AdBlock.
  2. Preferably also add aria-hidden="true" to not show this fake ad to users who use accessibility tools.
  3. Once the page is loaded, check whether this fake advertisement div is visible or not.
<div class="ad-box" style="position:fixed;top:0;left:0;" aria-hidden="true">
  &nbsp;
</div>
<script>
  setTimeout(function () {
    var adBoxEl = document.querySelector(".ad-box")
    var hasAdBlock = window.getComputedStyle(adBoxEl)?.display === "none"
    // ... save to DB
  }, 2000)
</script>

The way most AdBlocks work these days is that they target specific CSS classes (like class="ad-box") and apply display: none on it. That way, the Ad disappears in your browser.

You can see all the CSS classes that are used for blocking in EasyList blocklist.