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Reference library · Digital attribution
Server-Side Attribution
Server-side attribution matches conversions to ad exposures by sending event data directly from the advertiser's server, or a server-side tag manager / CDP, to the ad platform via API call, rather than firing a pixel from the user's browser. Because the match uses server-held identifiers such as order IDs, hashed customer data, or first-party cookies, it survives ad blockers, Safari's ITP, and cookie consent refusals that break browser pixels. Analysts run it alongside or in place of client-side pixels to recover conversions the browser method misses.
Worked example
A Czech e-commerce advertiser logs 9,600 purchases in a month. The browser pixel matches 5,760 of them to an ad click, a 60% match rate, because Safari and Firefox block roughly a third of traffic and ad blockers catch more. After adding server-side Conversions API calls keyed to a shared event ID, the platform matches 8,832 of the same 9,600 purchases, a 92% match rate, recovering 3,072 conversions the pixel alone missed. For the plan this means true cost per acquisition is materially lower than the pixel-only number suggested, and budget that looked wasted on underperforming placements was in fact converting.
How it is used
Instead of a formula, the analyst tracks matched volume: total conversions logged server-side versus the subset the platform can match to a click or impression ID, reported as a match rate. It's implemented through each platform's server-side API, Meta Conversions API, Google Enhanced Conversions, TikTok Events API, run in parallel with the existing pixel during a validation window, then used to replace or supplement it once match rate stabilizes above the pixel baseline. The common failure is going live with both pixel and server-side events firing for the same conversion without a shared event ID, so the platform has no way to tell they're the same order.
The common mistake
Don't run pixel and server-side events for the same conversion without a shared event ID; without deduplication the platform counts the order twice and inflates reported conversions and ROAS.