An A/B testers guide to Google Optimize implementation
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Implementation of Google Optimize Prerequisites DataLayer best practices Code snippet placement best practises Anti-flicker Snippet Timeout Which method to choose? Preferred method - Using the Optimize snippet Step 1 – Get the Optimize snippet Step 2 – Add the anti-flicker snippet Step 3 – Put it all together and add the code to your web pages Placement order Example #1 - Preferred method Alternate method – via Google Tag Manager Step 1 – Configure the Optimize Tag in Tag Manager Step 2 – Add the anti-flicker snippet Step 3 – Put it all together and add the code to your web pages Placement order Example #2 - Alternate method: GTM Method 3 - Using modified Analytics.js tag Step 2 – Add the anti-flicker snippet Step 3 – Put it all together and add the code to your web pages Placement order Example #3 - Analytics.js method Method 4 - Using modified GTAG Step 1 – Modify the global site tag Step 2 – Add the anti-flicker snippet Step 3 – Put it all together and add the code to your web pages Placement order Example #4 - Gtag method Removing an Optimize installation Using GTM Using analytics.js for both Optimize and Analytics Using analytics.js for Optimize and GTM for Analytics Using gtag.js for both Optimize and Analytics Using gtag.js for Optimize and GTM for Analytics Next step
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Implementation of Google Optimize
Optimize allows you to A/B test variants of web pages and see how they perform against a goal that you specify. It monitors the performance of your experiment, and tells you which variant is best.
Google’s recommendation is to add the so called anti-flicker snippet to your website. This makes the website invisible while the active experiment loads. We at Conversionista strongly encourage that you add this to your website to avoid any form of flickering (also sometimes called FOOC flash of original content).
We will cover how you implement the anti-flicker snippet further down in the white paper. More general information on the anti-flicker snippet is to be found at Google’s official support section.
Prerequisites In order to continue this guide you will need an account for the following tools:
● Google Analytics ● Google Tag Manager ● Google Optimize
Also have your Analytics tracking ID and your Optimize container ID at hand. They should look like this:
● Analytics tracking (property) ID: UA-XXXXXXXX-X ● Tag manager container ID: GTM-YYYYYY ● Optimize container ID: GTM-ZZZZZZ If you have trouble finding any of the IDs, click the links above to see the official documentation for each tool.
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DataLayer best practices When working with the page template, always use this method to check and interact with the dataLayer. This helps you to avoid a horrible mistake. The official GTM documentation suggests that the dataLayer should be declared before the GTM snippet is initialized. Like this:
This is not the best practice. Having one declaration works fine but when there are several declarations on the page, the last assignment completely overwrites the current datalayer. Or in other words, every time you make this declaration you replace the old dataLayer with a new empty one.
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NOTE To avoid this you should always use the push() method to interact with the dataLayer.
window.dataLayer = window.dataLayer || []; window.dataLayer.push({ 'var' : 'val' });
The first line checks if the global variable has been declared or not, if it has not the first line assigns a new empty array to it. This ensures that the following push() on line 2 always will work.
1. In the beginning of the page template always check whether the dataLayer has been defined or not or initialize it as a new Array if necessary 2. Always use the push() method when interacting with the dataLayer For more in-depth information on this specific topic, please read this blog post by Simo Ahava. Also, please read the official Tag Manager documentation on how to avoid other common pitfalls.
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Code snippet placement best practises Generally the code placement order should be as follows:
1. Any JavaScript (e.g. jQuery) that you wish to use in Optimize experiments. We recommend that you keep these to a minimum. 2. Initialization of any variables needed for targeting (data layer, JavaScript, cookies, etc). 3. Anti-flicker snippet. 4. Optimize snippet 5. Tag Manager container snippet. 6. Other JavaScript, trackers, and ad tags.
The code examples further down in this guide follow these general recommendations1 (by Google) on how to add code to your website.
1. The anti-flicker snippet should be placed immediately before the Optimize snippet (after the declarations). 2. If using gtag or analytics.js tags (method 3 and 4 below), move your Google Analytics tracking code up to the
, if it's not already there. It should immediately follow the anti-flicker snippet, if possible. 3. The following should come before the Optimize snippet: ○ ○ Data layer initialization. ○ Setting cookies. ○ Any scripts that you may want to use or that declare JavaScript variables that you wish to use in Optimize experiments. For example, jQuery and JavaScript used to target an Optimize variant. ○ Anti-flicker snippet4. The following should come after the Optimize snippet: ○ Other trackers, analytics tags, ad tags and/or tags deployed by a tag-management system. ○ Other scripts that you won’t target Optimize experiments against.
1 https://support.google.com/optimize/answer/9692472 Revised Thur May 14 2020 08:11:20 GMT+0200 (CEST)
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Anti-flicker Snippet Timeout The Optimize anti-flicker snippet supports the loading of your Optimize container asynchronously while hiding the page until the container is ready, ensuring that users don't see the initial page content prior to it being modified by an experiment. More in-depth information on the anti-flicker snippet is found here.
The timeout default value is set to 4000 milliseconds, which might be too high since many users expect a website to load under two seconds and up to 40% of the users will abandon a page if it loads over 3 seconds2.
Check your Google Analytics what your average page load time is. If you have trouble interpreting the results, please refer to the official documentation. If your website’s Avg. Document Interactive Time or Avg. Document Content Loaded Time is way over 2 seconds you have a site speed problem on your website.
To change the default amount, update the number passed at the end of the snippet. From a usability perspective 2000 ms is a good start. If you know that you’ve worked on your website performance you can go lower than that.
2 Based on the feedback of over 1000 online shoppers that were surveyed by Forrester Consulting https://www.hobo-web.co.uk/your-website-design-should-load-in-4-seconds/
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Which method to choose? There are two main installation methods for implementing Google Optimize:
1. Using the Optimize snippet (optimize.js) - Preferred 2. Through Google Tag Manager, GTM
The above methods are recommended for all new implementations. There are also two additional implementation methods if you deploy Google Analytics using the global site tag (gtag.js) or using Universal Analytics (analytics.js):
3. Using the analytics.js library 4. Using the global site tag, gtag.js
To remove previous Optimize installations before using the new recommended method, go to Removing an Optimize installation.
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Preferred method - Using the Optimize snippet To run Optimize experiments, you have to add the Optimize snippet to your page. By using this method, you add the optimize.js snippet directly on your page. The optimize.js snippet is a line of code that loads the specified Optimize container.
When you deploy the Analytics tag through GTM, it is still recommended that you install the Optimize snippet directly on the page (as opposed to deploying Optimize through a tag in GTM). You do not have to modify your Analytics tags in GTM. Also you don’t need any Optimize tag in GTM.
Step 1 – Get the Optimize snippet First, get the Optimize snippet code. It can be found under Settings in your Google Optimize container. Example:
Where GTM-XXXXXX is your Google Optimize container ID.
If you want to load Optimize asynchronously, add async to the snippet. Example:
Loading the script asynchronously means that it loads in parallel with other site content, instead of loading sequentially before content placed below it on the page. While the asynchronous snippet has the least impact on the rendering speed of your page, it has a greater risk of causing page flicker. If deciding to use the asynchronous script, the anti-flicker snippet should always be used.
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Step 2 – Add the anti-flicker snippet While this is optional, it significantly reduces the risk of page flicker and helps provide a better user experience especially to users on slow connections. Experiment variants will be shown only when the Optimize container loads within a certain period of time (under two seconds in this example). Google has designed this snippet to be as performant as possible.
Note: If you are using Activation events who don't fire changes on the first load you don't need the anti-flicker snippet.
Where GTM-XXXXXX is your Google Optimize container ID.
Step 3 – Put it all together and add the code to your web pages Final step is to add it to your web pages. Down below is an example where everything is put together according to the latest recommendations by Google.
Placement order This placement order follows the tagging best practices discussed in Code snippet placement best practises above. 1. Meta charset (UTF-8) 2. (jQuery and/or other JavaScript dependencies) – Optional 3. (dataLayer) – Optional 4. Google Optimize Anti-flicker Snippet 5. Optimize snippet 6. Google Tag Manager (js) 7. Google Tag Manager (iframe)
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Example #1 - Preferred method
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Alternate method – via Google Tag Manager When Optimize is served via Google Tag Manager, the GTM container must be loaded before the Optimize container. The result is that Optimize experiments only execute after both the GTM and Optimize containers are loaded.
Step 1 – Configure the Optimize Tag in Tag Manager Once you have the container IDs mentioned under prerequisites, follow the Tag Setup Guide for Optimize in Google Tag Manager:
1. Click Tags → New. 2. Change the default name of "Untitled Tag" to a descriptive title, such as "Optimize - www.example.com"
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3. Click Tag Configuration → Google Optimize. 4. Enter your Google Analytics Tracking ID and your Optimize container ID (a.k.a. the Optimize snippet ID, available in the Optimize Container setup panel.) 5. Click More settings, and configure the Fields to Set and Advanced Configuration with the same values as your Google Analytics tags. 6. Click Save, and proceed to save the tag without triggers.
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7. Open any Google Analytics Page View tags that are being triggered on load of pages where you want the Google Optimize tag to be fired. 8. Click to edit the Tag Configuration, and open Advanced Settings → Tag Sequencing. 9. Check the box to fire a tag before this tag fires, and select your Google Optimize tag as a “Setup Tag”. 10. Click to Save your Google Analytics Page View tag, and repeat on any other Google Analytics Page View tags as relevant. The goal is to fire Optimize on every page where you want to be able to run an experiment.
The above procedure makes sure that Optimize fires before any Page View tags, thus minimizing potential flickering or delay.
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Step 2 – Add the anti-flicker snippet While this is optional, it significantly reduces the risk of page flicker and helps provide a better user experience especially to users on slow connections. Experiment variants will be shown only when the Optimize container loads within a certain period of time (under two seconds in this example). Google has designed this snippet to be as performant as possible.
Where GTM-XXXXXX is your Google Tag Manager container ID.
Step 3 – Put it all together and add the code to your web pages Final step is to add it to your web pages. Down below is an example where everything is put together according to the latest recommendations by Google.
Placement order This placement order follows the tagging best practices discussed in code snippet placement best practises above. 1. Meta charset (UTF-8) 2. (jQuery and/or other JavaScript dependencies) – Optional 3. (dataLayer) – Optional 4. Google Optimize Anti-flicker Snippet 5. Google Tag Manager (js) 6. Google Tag Manager (iframe)
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Example #2 - Alternate method: GTM
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Method 3 - Using modified Analytics.js tag If you implement Google Analytics by using the analytics.js tag directly on your page, you can add a line of code to your Analytics tag that loads the specified Optimize container.
Step 1 – Modify the Analytics tracking code First, modify the Google Analytics tracking code. Example:
Where UA-ZZZZZZZZ-Z is your Google Analytics property ID and where GTM-XXXXXX is your Google Optimize container ID.
If you have implemented Google Analytics through GTM, but still want to add Optimize with a modified Analytics.js tag, both tags need to have the same custom Analytics settings. If your Analytic tag in GTM has custom Analytics settings, you must add the same customizations to the Analytics tracking code, e.g. if you want to add cross domain tracking. You can find custom Analytics settings under “Fields to Set” in your Analytics tag in GTM.
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The custom Analytics settings that must have the same values in GTM and the modified Analytics tracking code are these ones3:
'clientId' 'sampleRate' 'siteSpeedSampleRate' 'alwaysSendReferrer' 'allowAnchor' 'allowLinker' 'cookieName' 'cookieDomain' 'cookieExpires' 'cookiePath' 'legacyCookieDomain' 'legacyHistoryImport' 'storeGac'
For example, if the tag in GTM looks like the screenshot above, then allowLinker and cookieDomain has to be added to the Analytics tracking code as well: ga('create', 'UA-ZZZZZZZZ-Z', 'auto', {allowLinker: true});
Note that cookieDomain could just be added as ‘auto’ as in the example above. The other settings should be added between curly brackets as allowLinker in the example above.
If you have several settings, you can list them within the curly brackets, separated by commas.
ga('create', 'UA-ZZZZZZZZ-Z', { allowLinker: true, cookieDomain: 'auto', sampleRate: 5, allowAnchor: false });
All the configurable field names can be found here.
3 https://support.google.com/optimize/answer/7359264?hl=en Revised Thur May 14 2020 08:11:20 GMT+0200 (CEST)
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Step 2 – Add the anti-flicker snippet While this is optional, it significantly reduces the risk of page flicker and helps provide a better user experience especially to users on slow connections. Experiment variants will be shown only when the Optimize container loads within a certain period of time (under two seconds in this example). Google have designed this snippet to be as performant as possible.
Step 3 – Put it all together and add the code to your web pages Final step is to add it to your web pages. Down below is an example where everything is put together according to the latest recommendations by Google.
Placement order This placement order follows the tagging best practices discussed in Code snippet placement best practises above. 8. Meta charset (UTF-8) 9. (jQuery and/or other JavaScript dependencies) – Optional 10. (dataLayer) – Optional 11. Google Optimize Anti-flicker Snippet 12. Google Analytics tracking code with Optimize 13. Google Tag Manager (js) 14. Google Tag Manager (iframe)
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Example #3 - Analytics.js method
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Method 4 - Using modified GTAG If you implement Google Analytics by using the gtag.js snippet, you can add a line of code to the gtag that loads the specified Optimize container.
Step 1 – Modify the global site tag You can find the gtag by navigating to Admin > Property column > Tracking Info > Tracking Code or modifying the tag below.
Add your Optimize Container ID to the gtag snippet and make sure you also have the right Google Analytics tracking ID. In the snippet above, change UA-ZZZZZZZZ-Z to the ID of the Google Analytics property and GTM-XXXXXX to your Optimize Container ID (can be found in Optimize under Container > Container setup > Install Optimize).
Step 2 – Add the anti-flicker snippet While this is optional, it significantly reduces the risk of page flicker and helps provide a better user experience especially to users on slow connections. Experiment variants will be shown only when the Optimize container loads within a certain period of time (under two seconds in this example). Google have designed this snippet to be as performant as possible.
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Step 3 – Put it all together and add the code to your web pages The final step is to add the code to your web pages. Down below is an example where everything is put together according to the latest recommendations by Google.
If you do not have the global site tag installed already, paste the code on every page where you want to be able to run Optimize, following the placement order in the list below.
If the global site tag is already installed, just add your Optimize Container ID to the tag as in the example in step 1, and make sure the tag and the anti-flicker snippet is placed according to the placement order below.
Only use one gtag per page. To use multiple gtag commands on one page, add 'send_page_view': false to all of the commands except one.
Placement order This placement order follows the tagging best practices discussed in Code snippet placement best practises above. 1. Meta charset (UTF-8) 2. (jQuery and/or other JavaScript dependencies) – Optional 3. (dataLayer) – Optional 4. Google Optimize Anti-flicker Snippet 5. Global Site Tag with Optimize ID 6. Google Tag Manager (js) 7. Google Tag Manager (iframe)
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Example #4 - Gtag method
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Removing an Optimize installation How to remove an old Optimize installation depends on how it was implemented.
1. Using GTM 2. Using analytics.js for both Optimize and Analytics 3. Using analytics.js for Optimize and GTM for Analytics 4. Using gtag.js for both Optimize and Analytics 5. Using gtag.js for Optimize and GTM for Analytics
Using GTM 1. Find your Google Analytics Pageview Tag for the Analytics property linked to your Optimize container. 2. Click on the tag to configure and go to Advanced Settings > Tag Sequencing. 3. Unclick “Fire a tag before Google Analytics Universal Analytics fires” for Setup Tag Google Optimize.
4. Find you Google Optimize Tag in GTM and delete it 5. Publish changes 6. Change ID in your anti-flicker code (if adding Optimize again through other method)
Where GTM-XXXXXX should now be your Optimize container ID instead of your Google Tag Manager container ID.
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Using analytics.js for both Optimize and Analytics If Google Analytics is implemented through the Analytics.js snippet (hardcoded on the page), remove this line from the snippet:
Using analytics.js for Optimize and GTM for Analytics If Google Analytics is implemented through GTM, remove the whole analytics.js snippet from the code in head. The snippet looks like this:
See Method 3 - Using modified Analytics.js tag
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Using gtag.js for both Optimize and Analytics If both Google Optimize and Google Analytics is implemented through the gtag (hardcoded on the page), remove this line from the snippet:
(see Method 4 - Using modified GTAG)
Using gtag.js for Optimize and GTM for Analytics If Optimize is implemented through the gtag, but Google Analytics is implemented through GTM, remove the whole gtag.js snippet from the code in head. The snippet looks like this:
(see Method 4 - Using modified GTAG)
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Next step When you have everything in place, go ahead and create your first experiments. If you don’t know where to start, check our blog post 3 things to start AB-testing.
Also, go ahead and read our white paper on how to add custom objectives in Google Optimize.
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