ClickTag Implementation for HTML5 Banners

The correct way to implement clickTag for Google Ad Manager, Campaign Manager 360, and other ad servers.

What is a ClickTag?

A clickTag is a JavaScript variable that ad servers use to track clicks on HTML5 banner ads. When a user clicks the banner, the ad server replaces the default URL with the campaign's click-through URL, enabling click tracking and dynamic destination URLs.

The Correct Pattern

Google Ad Manager scans the <head> section of your HTML for a specific pattern. Here is the correct implementation:

<!DOCTYPE html>
<html>
<head>
  <meta name="ad.size" content="width=300,height=250">
  <script type="text/javascript">
    var clickTag = "https://www.example.com";
  </script>
</head>
<body>
  <div id="banner" onclick="window.open(window.clickTag)">
    <!-- Your banner content -->
  </div>
</body>
</html>

Key rules: The var clickTag declaration must be (1) in the <head>, (2) a global variable, (3) named exactly clickTag (case-sensitive), and (4) not minified or obfuscated.

How GAM Processes ClickTag

You upload the HTML5 ZIP to Google Ad Manager
GAM scans the <head> for var clickTag = "..."
If found, GAM shows "ClickTag detected" in the creative preview
At serve time, GAM replaces the default URL with the click-through URL from the line item
Clicks are tracked through GAM's redirect system

Common Mistakes

clickTag inside <body>

GAM only scans <head>. If your clickTag declaration is in the body, it won't be detected.

<!-- WRONG: clickTag in body -->
<body>
  <script>var clickTag = "https://example.com";</script>
</body>

<!-- CORRECT: clickTag in head -->
<head>
  <script>var clickTag = "https://example.com";</script>
</head>

clickTag inside a function or IIFE

The variable must be global. Wrapping it in a function, IIFE, or module makes it invisible to GAM.

<!-- WRONG: not a global variable -->
<script>
(function() {
  var clickTag = "https://example.com";
})();
</script>

<!-- CORRECT: global variable -->
<script>
var clickTag = "https://example.com";
</script>

Using let or const

Some ad servers specifically look for var. Using let or const may not be detected.

<!-- WRONG: may not be detected -->
<script>const clickTag = "https://example.com";</script>

<!-- CORRECT: use var -->
<script>var clickTag = "https://example.com";</script>

Minified or obfuscated code

GAM uses regex pattern matching. If your build tool minifies the variable name or restructures the declaration, detection fails.

Missing ad.size meta tag

GAM needs the ad.size meta tag to know the banner dimensions. Without it, the creative may not display correctly.

<meta name="ad.size" content="width=300,height=250">

Click Handler Best Practices

Always use window.open(window.clickTag) instead of just clickTag — this ensures the global variable is used even if there's a local scope collision:

<!-- Best practice -->
<div onclick="window.open(window.clickTag)">...</div>

<!-- Also works -->
<script>
document.getElementById('banner').addEventListener('click', function() {
  window.open(window.clickTag);
});
</script>

Platform Differences

Platform	Variable Name	Detection Method	Notes
GAM	clickTag	Regex in <head>	Most common. Requires var declaration.
CM360	clickTag	Enabler API	Uses Enabler.exit() for click tracking.
DV360	clickTag	Enabler API	Same as CM360.
Sizmek	clickTag	EB.clickthrough()	Sizmek SDK required.

Debugging ClickTag Issues

Check GAM creative preview: Upload your ZIP and check if "ClickTag detected" appears
View source: Open the HTML file and verify var clickTag is in <head>
Browser console: Open the banner in a browser and type window.clickTag — it should return the URL
Click test: Click the banner and check if window.open is called with the correct URL

Skip the manual work: Our Banner Generator handles all of this automatically. Upload your video, and the clickTag is correctly implemented in every export.