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How AdWords tracks website conversions

This article provides more information about how we measure the interactions that people had with your ads before a conversion, including some guidelines to make sure you can measure conversions from all browsers.

When people interact with your ads (by clicking a text ad or viewing a video ad), AdWords stores a cookie on a Google domain that contains information about the interaction. When someone converts on your website, the conversion tracking tag you installed reads this cookie and sends it back to AdWords with the conversion information. In some cases, the cookies we use to store information about your ad interactions may not be available due to factors including browser settings. In these cases, AdWords offers the following ways to track conversions from clicks more accurately.

Before you begin

For the most accurate measurement, you’ll need a site-wide tag (see the options for implementing it below). Before you implement it, make sure to follow these instructions:

  1. Turn on auto-tagging in all your AdWords accounts.
  2. If you use any click-trackers in your tracking URLs, make sure they pass on the GCLID ("Google click identifier") to your landing pages.
  3. Don’t fire your tags from within an iFrame (example: within another tracking tag like Floodlight).

Ways to track conversions

Review the following options to implement a site-wide tag that sets new cookies on your domain, which will store information about the ad click that brought someone to your site:

Option 1: Track your conversions with the new AdWords conversion tracking tag

To ensure that AdWords can measure all of your conversions, regardless of the browser that your site visitor is using, we recommend that you use the new AdWords conversion tracking tag. This tag consists of a global site tag and an event snippet. This tag sets new cookies on your domain that will store information about the ad click that brought people to your website. The cookies receive the ad click information from a GCLID (“Google click identifier”) parameter that is included in the conversion tracking tag.

For the new conversion tracking tag to work, make sure you follow the instructions in Before you begin.

You’ll find the code snippets for the new conversion tracking tag when you set up conversion tracking for your website in the new AdWords experience.

How to opt out

If you don’t want the global site tag to set first-party cookies on your site’s domain, add the highlighted portion below to your global site tag’s config command:

 gtag('config', 'AW-123456789', {'conversion_linker': false}); 

We don’t recommend doing this as it will lead to less accurate conversion measurement.

Option 2: Use Google Analytics

You can install a Google Analytics tag on your website. If you followed the instructions in Before you begin, the GCLID for an ad click will be stored in a Google Analytics cookie on your site’s domain. If you’ve set up your accounts and tag correctly, the AdWords conversion tracking tag will be able to use the GCLID from the Google Analytics cookie. In this case, no conversion modeling is necessary.

To use this method of tracking website conversions, follow the instructions in “Before you begin,” then follow these additional guidelines:

If you follow these steps, we’ll automatically read the GCLID from the Google Analytics cookie. If you don’t want Google Analytics to store the GCLID in this cookie, follow the instructions in How to opt out below.

Note that the Google Analytics cookie only stores the GCLID for the last click. If there are multiple AdWords accounts driving traffic to your website and you are currently not using cross-account conversion tracking, this can lead to lower conversion numbers.

How to opt out

To opt out of using the Google Analytics cookie to store the GCLID, follow these instructions to update your Google Analytics tag. We don't recommend doing this as it will lead to less accurate conversion measurement.

Option 3: Use Google Tag Manager with the new conversion linker tag

Google Tag Manager allows you to quickly and easily deploy and update tags on your website without changing the code on your page. To ensure that your AdWords conversion tracking tags receive the necessary ad click information, also follow these steps:

  1. In your Google Tag Manager container, click to add a New Tag.
  2. Click Tag Configuration and select the Conversion Linker tag type.
  3. Click Triggering and select a trigger to have the tag fire on All Pages.

The Conversion Linker tag automatically detects the information about the ad click that brought someone to your site in the landing page URLs and stores this information in new cookies on your domain.

If you're new to Google Tag Manager, read more about getting started.

When AdWords can’t observe all conversions

If you don’t use any of the options above, the cookies we use to store information about your ad clicks may not be available due to factors including browser settings. If you use the previous conversion tracking tag with the default JavaScript code, we’ll be able to track conversions for users who have interacted with Google services and domains recently, and we’ll include those conversions in your reports. 

If you’ve manually removed the JavaScript code from the conversion tracking tag, in those cases where the cookie information is unavailable, we may be unable to track conversions for those users who have interacted with Google services and domains recently.

In order to measure these conversions, we strongly recommend that you use the default JavaScript code when using the previous conversion tracking tag. 

In addition, if you don’t use any of the options above, we will soon also include modeled conversions in the “Conversions” column in your reports to estimate conversions that we’re unable to measure. To generate these modeled conversions, AdWords will use current and past data on the number of people who have interacted with your ads and later converted on your website. These additional modeled conversions will only be available for same-device conversions for Google Search and Shopping ads. They will not be available for Display, Video, and AdSense for Search, and for Display or video view-through conversions, or for cross-device conversions. Please note that the modeled conversions will appear in your reports as we roll out this feature.

There may still be times when we are not able to measure conversions for Video. For example, when a user views a video ad in the YouTube mobile app and later converts in the mobile browser, but has not signed into Google services on either. In these cases, we will include modeled conversions in the “Conversions” column in your reports to estimate conversions that we’re unable to directly measure. To create these modeled conversions, we use aggregated and anonymized data from users who have previously signed into Google services.

Impact to bidding

We recommend that you monitor your conversion reports over the next few months and consider making any necessary changes to your bids. If you’re using Target CPA or Target ROAS Smart Bidding strategies and you notice a decrease in traffic, you may want to adjust your targets during this time to compensate for the underreported conversions. If you’re setting bids manually, keep in mind that some conversions might not be reported when you’re evaluating performance and adjusting bids.

Informing your site visitors about data collection

As always, please ensure you're providing users with clear and comprehensive information about the data you collect on your websites, and getting consent for that collection where legally required.

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