A Conversions API is a server-to-server connection that sends conversion events from your systems directly to an ad platform. No browser in the middle. That is the whole idea, and it is worth understanding properly because every major platform now runs its measurement through one.
Why pixels stopped being enough
For fifteen years the pixel did the job. A snippet in the page fired when someone purchased, the platform recorded it, attribution worked. Then browsers started blocking third-party tracking, ad blockers spread, and iOS capped cookie lifetimes to days. The pixel still fires, but it misses a growing share of what actually happens. Platforms noticed they were optimizing on partial data, and partial data trains bad models.
The fix was to stop depending on the browser. Send the event from a server instead: your commerce backend knows about the purchase whether or not the browser cooperated.
The same idea, per platform
Meta calls it the Conversions API, CAPI. Events go to Meta with hashed identifiers (email, phone) and an event ID that deduplicates against the pixel. Meta also offers CAPI Gateway and Signals Gateway, self-hosted infrastructure for the same pipe.
Google splits the job across products. Enhanced Conversions supplements the Google tag with hashed user data. Enhanced Conversions for Leads and Offline Conversion Import bring CRM and offline outcomes back to the click. Store Sales handles in-store transactions. The Data Manager API is the newer unified entry point for all of it.
Snap and TikTok run CAPI and the Events API respectively, both covering web, app, and offline events. Pinterest, LinkedIn, X, and Reddit each operate their own conversions API with the same shape: server-side events, hashed identifiers, dedup against their tag.
What a good implementation has
Four things, on any platform. Deduplication, so pixel and server events do not double count. Hashing at source, so raw PII never travels. Consent awareness, so a user’s choice actually controls delivery. And match feedback, so you can see whether the platform recognized the people behind your events.
Does it work?
The published numbers are consistent in direction. Meta advertisers running pixel plus CAPI see lower cost per action than pixel alone; KFC measured 5% additional purchases with the combination. Google reports median uplifts of about 5% on Search and 17% on YouTube for Enhanced Conversions. The mechanism is the same everywhere: more complete signal, better attribution, better optimization.
One integration through Signals covers all of the above. That is the product pitch in one sentence, and this article was the long version.