Have you heard of Google Tag Manager (GTM) measurement, which runs on a server? And did you know that it is the ideal way to speed up your website loading, increase your users’ privacy, or improve attribution evaluation for your marketing campaigns? Join us to find out what server-side measurement is good for and how it differs from classic measurement.
How standard measurement works
Most websites today use Google Tag Manager (GTM) to manage measurement. The GTM code is inserted into the HTML of the website, and when a user visits the website, the following happens:
- The client browser (i.e., the website visitor’s browser) downloads the GTM code.
- The browser processes the GTM code and runs other measurement codes from individual platforms (Facebook, Sklik, etc.) to which you want to send data from the website.
- Most of the measurement codes from individual platforms run in this way download their own JavaScript code, which then finds and processes the data it needs and sends it to its platform.
Some measurement codes also wait for user actions on the website (such as downloading a file, scrolling, submitting a form) and then trigger further measurements.
As mentioned above, all of this runs in the client browser, which puts a relatively heavy load on it. Even basic measurement codes on websites are at least 20 KB per platform, but Facebook, for example, downloads as much as 130 KB of data when loading a website.
Processing takes some time, and sending increases the amount of data used by the page. This is a problem for many reasons – it slows down the loading of the website (especially on slower devices or mobile phones, the slowdown can be significant), it increases the volume of downloaded data (users with mobile phones with limited monthly data allowances will not thank you for this), it worsens your search ranking (speed is one of the key attributes for SEO), and measurement scripts have access to all information on the website and can theoretically do anything with it (even if it is personal data).
What is server-side measurement?
As the name suggests, server-side measurement is a way of using GTM where GTM is not part of the HTML page and does not run in the user’s browser. Instead, it runs on a server, such as Google Cloud. It is only on this server that the individual measurement codes are run.
The standard GTM remains in the client browser, which sends data to the server-side GTM. Only then does it handle sending data to platforms such as Google Analytics, Facebook, etc.
To run server-side GTM, you always need a machine—either your own or one in the cloud. And you need to adjust your measurement settings.
In addition to not forcing the user’s browser to download and send a lot of data, there are a number of other advantages that might interest you. Let’s take a closer look at them.
What are the advantages of server-side GTM?
Speed
Speed is generally very important for websites. Google has been mentioning it for years as one of the factors that influence a website’s position in search results. Fewer measurement codes on a page means higher speed and thus better search rankings and more visitors. By the way, try testing how much time it takes to process measurement scripts on your website using PageSpeed Insights – look for information about third-party code:
Example of how much time it takes to start loading measurement codes on a Alza.cz website
Data protection
If you enter sensitive data on a page (e.g., phone number, address, etc.), third-party scripts (Facebook, Sklik, etc.) embedded in standard GTM may have access to it. On the other hand, when measuring in server-side GTM, you can be sure that they will not access any data other than what you explicitly provide them with. This is because individual platforms only communicate with GTM on the server and cannot access the “raw” data collected by GTM in the client browser.
And by the way, whether we like it or not, platforms always see at least the user’s IP address. If you use server-side GTM, platforms cannot access it unless you provide it to them.
Reasonably set Content Security Policy
Your website can use Content Security Policy (CSP) security settings. This typically applies to websites that work with sensitive or personal data. This setting tells the browser which domains (Facebook, Google Analytics, Sklik, etc.) it can download and run scripts from. And you have to list them all here. Can you see the problem? If you use multiple platforms, your CSP settings might look like this:
And if you happen to forget to update something, oops…
In such cases, managing all domains is complicated, and it is easy to forget to add or remove something. By using GTM on the server, the list of domains is shortened, saving you some of the hassle.
Security
If you deploy a script on your website, it can do a lot of things to your website. Including unpleasant things such as changing the content of the website, redirecting it to another website, or sending sensitive data from the website to China. This can happen by mistake or through negligence. And believe us, we’ve seen plenty of similar things. This cannot happen with server-side GTM because the codes are on the server and cannot reach the user’s browser at all.
Data validation or enrichment
If you want to validate and correct data in some way, you have extended options in server-side GTM. This is also a suitable solution if you want to enrich data, e.g., with margins on specific products. Typically, you do not want to send this to platforms from client-side GTM, where anyone can access such information.
Data retention for attribution evaluation
If you are a marketer dealing with attribution over a longer period of time, switching to server side may be an advantage for you. Some browsers (Safari or Firefox) typically aggressively delete cookies that are not httpOnly (i.e., it is clear that they are intended for marketing purposes and not for the technical functioning of the website) after 1 or 7 days. On the server side, you store such cookies yourself, so you don’t have to worry about losing data from customers using stricter browsers.
100% data measurement
If you wish, you can send data to server-side GTM directly from the server rather than from the client browser (see image below). This allows you to access virtually all data.
Please note, however, that when processing personal data, you must still comply with GDPR and respect the user’s wish not to be measured. In other words, it is not appropriate to bypass user consent by downloading data directly from the web server.
Why not server-side GTM?
Of course, there are also disadvantages to using server-side measurement.
- Price – as mentioned above, in order to run server-side GTM, you always need a machine – either your own or in the cloud. Both approaches cost money. With Google Cloud, for example, the price will most often range from free (for small websites) to $1,000 per month (for websites with tens of thousands of visits per day). On top of that, you have to add the costs of commissioning and more complex measurement adjustments, which require a programmer or analyst.
- It does not work for all platforms—not all platforms currently support server-side measurement and require browser execution, such as Sklik. Among frequently used platforms, server-side measurement is supported by Google Analytics, Facebook, Mailchimp, and several others. So you often end up in a situation where only part of the code is in the server container, while the rest remains in classic GTM. However, even just part of the measurement running on the server side may make sense for you – consult with your analyst.
We assume that in the future, support for the platform will bem přibývat a server-side bude dávat čím dál větší smysl.
Does this make sense to me?
Can’t imagine if this is for you? We think it definitely is if:
- You send data to a large number of platforms (most often different GA accounts), which slows down your website.
- You need to work with extremely sensitive data (e.g., social security number, ID card number, etc.) and want to protect it.
- Many of your visitors use Safari or Firefox, which complicates long-term attribution.
- You need to operate with product margins in your evaluations.
- You need server measurement codes (typically for affiliate platforms), but you don’t want to bother programmers with it all the time.
Do you see yourself in some of these cases, but you’re still not sure if a server-side solution is right for you?
Let us know! We will discuss the pros and cons in your case with you, and if it makes sense, we will be happy to help you set up server-side measurement.