Pixels and tags: how the advertising tools measure what visitors do

What a pixel is#

A pixel (or tag) is a small script from an advertising company that runs when someone visits your website. It sends what the visitor does (page view, contact form, purchase) to the advertising system. That is why you can see which ads brought customers and show ads to people who have already been on the page. Without a pixel, the advertising system only sees the click, not what happened next.

Pixels store or read information in the visitor's browser. That is why consent is required before they load, read Cookies and consent.

The most common tools and their IDs#

• Meta Pixel (Facebook and Instagram): a numeric ID. The script is fetched from connect.facebook.net [1].
• The Google tag (Google Analytics 4 and Google Ads): a tag ID that starts with G-, AW- or GT- [2] [3].
• Google Tag Manager: a container that starts with GTM-. It is used when you want to manage many tags yourself [4].
• LinkedIn Insight Tag: a partner ID in digits [5].
• TikTok Pixel: an ID that you get in TikTok Ads Manager [6].
• Microsoft: the UET tag for Microsoft Advertising [7] and Clarity for visitor analytics [8].

How it is done right#

• Only the ID, not the code. If you paste in ready-made code, it easily goes wrong: duplicates, old versions or code that loads before the visitor has said yes. In your admin at NOVAI you only enter the ID; we add the code.
• Once per tool. The same pixel twice counts every visit twice.
• Allowed in the security rules. A website with a security policy (CSP) must explicitly allow the tool's addresses, otherwise it is silently stopped [9] [8]. We take care of that.
• Only after consent. Meta describes how the pixel is kept switched off until the visitor has consented (fbq('consent', …)) [10], and Google controls its tags with Consent Mode [11].
• The server side as a complement. Meta's Conversions API and Google's tag gateway send events through your own server. They make the measurement more stable, but do not replace consent [12] [13].

This is what we do#

• In the admin, under Measurement and ads, you enter the IDs for Meta, Google, Tag Manager, LinkedIn, TikTok and Microsoft. We check the format, add the right code once, allow the right addresses in the security policy and add a consent box.
• No tool loads before the visitor has said yes. If the visitor says no, it never loads.
• The privacy policy on your website is updated automatically with which tools are used and why.
• In the analysis of your current website you see which pixels there are and whether they load without consent.