Now, here’s where things get properly interesting — and by interesting, I mean “likely to cause tracking discrepancies that will haunt your dreams.”
Conversions can happen in two fundamentally different places: in the browser (client-side) or on the server (server-side). This distinction matters rather more than most people realize.
Browser-based conversions are tracked by JavaScript running on the visitor’s device. When someone clicks that “Add to Cart” button, a clever little script fires off an event to Google Analytics, Meta Pixel, or whatever tracking monstrosity you’ve bolted onto your website. This is how most tracking has worked since the dawn of digital advertising, back when browsers were simple and innocent creatures that actually respected tracking cookies.
The problem? Browsers have become decidedly less cooperative. Privacy features like Intelligent Tracking Prevention make cookies expire faster than milk in the sun. And users may alternate between using their phone and desktop, turning your sophisticated tracking infrastructure into digital confetti. Everyone likes to talk about it. After all, what can be easier than blaming Apple for missing data?
But you know what is a real problem with browser conversions? Conversions happening on the server or offline inherently. Closed won CRM deals, trial subscriptions transitioning to paid, recurring payments. Even in simple e-commerce purchases the actual conversion is when the e-commerce platform is notified of a completed payment; tracking a browser events on a thank-you page would track just that — a page being viewed by the user — which may not happen at all, or may happen multiple times.
Server-side conversions happen where users can’t interfere with them — on your server, naturally. When a purchase completes, your server knows about it because, well, it’s processing the transaction. No JavaScript required. No browser cooperation needed. Just your server sending a polite notification to your analytics platform saying, “Yes, this definitely happened, I was there.”
The catch? Server-side tracking requires actual development work. The problem is, server events don’t know anything about the ad click and visit that led the visitor to the website. You need to attribute them to clicks, set up APIs, authenticate connections, handle errors gracefully, and generally do all the things that engineers do while muttering under their breath about marketing’s “simple requests.”
(Or just use proper server-side tracking software like Able CDP, but let’s not get distracted.)
In the next chapter Connect we discuss what data each platform expects and how to make sure they receive all the data they need.