Duplicate GA4 Tags and Two GTM Containers: Why Conversions Are Counted Twice

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Duplicate tags are easy to miss because nothing looks broken. Reports are full of data, conversions are coming in, and the numbers even look good. In our check of 640 European webshops, 1 in 25 loaded more than one Google Tag Manager container, one of the most common sources of duplicate data.

How duplicates happen

Most duplicates come from adding tracking in a second place without removing the first:

  • GA4 through a WordPress plugin (Site Kit, PixelYourSite, a WooCommerce analytics plugin) and again through Google Tag Manager,
  • an old gtag.js snippet in the theme header, plus GTM added later by an agency,
  • two GTM containers on the same page, for example one from the previous agency and one from the current one,
  • the Meta pixel or Google Ads tag installed by a shop module and again in GTM.

Signs in your reports

  • Page views per session are about twice what you would expect.
  • Engagement rate is unusually high or bounce rate unusually low.
  • The number of purchases in GA4 is higher than the number of orders in the shop.
  • In Google Ads, conversions jump after a website change without any change in campaigns.
  • In GA4 DebugView, every page load produces two page_view events.

How to check it

  1. Open the website, open the developer tools and go to the Network tab.
  2. Filter for collect?v=2. These are GA4 requests.
  3. Reload the page. If you see two requests for page_view with the same measurement ID (tid=G-...), GA4 is installed twice.
  4. In the page source, search for googletagmanager.com/gtm.js and gtag/js. Count the containers and GA4 IDs.

Tag Assistant shows the same information in a clearer way: it lists every container and Google tag on the page.

How to clean it up

  1. Choose one source. In most cases that is Google Tag Manager, because it keeps all tags in one place with version history.
  2. Remove the others: disable GA4 in the plugin settings (in Site Kit, disconnect Analytics or switch off the tag snippet), remove old code from the theme, and remove the extra GTM container once you have moved anything useful from it.
  3. Check Google Ads conversions separately. A common duplicate is a Google Ads conversion tag together with the same conversion imported from GA4. Only one of them should be set as the primary action used for bidding.
  4. Test the purchase or form submission once more and confirm that one action produces one event.

What happens to your numbers

After the cleanup, page views and conversions will drop. That is the real level, not a loss. Put a note in GA4 with the date of the change so nobody later compares the new numbers with the inflated old ones. If smart bidding used the duplicated conversions, expect a short adjustment period in Google Ads and Meta.

Want to know if anything on your website is sent twice? A tracking audit checks every container, tag and conversion action.