Make every conversion count with sitewide tagging

August 2, 2018

There has never been a more exciting time to be a digital marketer. From second-screening during a commercial break to searching at a bus stop, there are more opportunities than ever to reach your customers. But, all of that access makes measurement difficult. Conversion measurement is getting more complex, and your site’s tagging needs to keep up.

The best way to measure online conversions is to use tools that set cookies in the same domain as your site (known as first-party cookies). The tags for such tools should be placed sitewide, on every page of your site, to effectively measure and optimize your digital marketing investment. It’s also recommended to use a dynamic library like gtag.js (also known as the global site tag) to maintain flexibility as your needs, and the industry, evolve.

With first-party measurement, you can measure what marketing and experiences work best across your sites. It’s important to use sitewide tagging solutions that can set first-party cookies for measuring conversions. You can do this type of tagging with Google’s global site tag (for Google Ads, Display & Video 360, Search Ads 360, Campaign Manager, and Google Analytics) or with a tool like Google Tag Manager (for all Google and non-Google tags)

Google’s tagging options

Google provides two options for conversion tagging: the global site tag or Google Tag Manager. With a single implementation, each of these work across Google's advertising and analytics products: Google Ads, Display & Video 360, Search Ads 360, Campaign Manager, and Google Analytics.

While the implementation for each of these solutions is slightly different, they both enable simple and consistent measurement. An update should take less than a day of your webmaster’s time to complete. When included on all pages of your website, either the global site tag or the conversion linker tag in Google Tag Manager will set new, first-party cookies on your domain so that you can measure the actions that you care about and understand which clicks result in conversions.

There are different reasons to choose each of the tagging options:

If you need more time before adopting one of these sitewide tagging solutions and you have already deployed a previous version of the Google Analytics tag across your site, you can link your Google Ads and Analytics accounts to ensure you are able to measure conversions using first-party cookies. Note that this solution only works for Google Ads conversion tracking and not Floodlight tags.

Understanding your data

Once your site is tagged, it’s important to understand and verify your data.

  • Compare your reported conversions with actual, hard sales. Your own sales figures are the best source of truth for your business. If online and offline numbers are significantly out of sync, take a look at your tagging to ensure things are set up correctly. Keep in mind that some discrepancies are expected due to differences in counting methodologies and technologies.
  • Understand how long it takes an average customer to convert. The “Days to Conversion” metric in Google Ads is one way to see how long people like to research before actually purchasing. The longer the gap between a click and a conversion, the likelier it is for that conversion to be underreported in Google Ads. Update your performance targets accordingly.

If you aren’t able to update your tags, you may begin to see some modeled conversions in your account starting later this year. Without updated tagging, Google Ads and Search Ads 360 will model conversions for same-device click-through conversions. This way you’ll still have an idea of your overall performance. For the most accurate measurement, especially in the more granular areas of your account like keywords, you’ll need to update your tags.

We recommend you update your tagging as soon as possible to preserve insights. As measurement using third-party cookies becomes less accurate over time, you might see a decrease in overall conversions, conversion rates, and conversion values. This doesn’t mean that your actual conversion volume is decreasing, it only means that you’re losing visibility. The quicker you act, the more insight you can preserve.


Sitewide, first-party tagging is vital to understanding your performance online. Please take the time to make this change to your tagging a priority; the longer you wait, the more you’ll lose insight. As you make these updates, ensure you're providing users with clear and comprehensive information about data collection, and obtaining consent from users where legally required. If you have any questions, please don't hesitate to reach out to your account team or contact us at any time.

Post by Russell Ketchum, Group Product Manager, Google Analytics

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