Sending conversions back to ad platforms
How pixels return your conversion data to Facebook and the other platforms, so their algorithms optimize toward buyers.
A pixel is how conversions get out of PostbackX and back to the ad platform. It is the opposite direction from a postback, and it is the step that changes what the ad platform's algorithm does.
Why it matters more than it sounds#
An ad platform optimizes toward whatever outcome you report. Report nothing and it optimizes for clicks, because clicks are all it can see — and the cheapest clicks come from people who click a lot and buy nothing.
Send conversions back and it can optimize toward people who actually convert. Same budget, different audience. This is usually the largest single improvement available to a new account, which is why it is worth doing before scaling spend.
Add one#
Go to Pixels and add a pixel for each platform you buy traffic on. The page has a How it works walkthrough.
For Facebook you need two values, both from Events Manager:
- The Pixel ID
- A Conversions API access token
Other platforms differ in detail; the page asks for what each one needs.
Once a pixel exists, assign it to your campaigns. Conversions then flow automatically — there is nothing further to maintain.
Server-side, not browser-side#
PostbackX sends conversions from its servers to the platform's API — for Facebook, the Conversions API, usually written CAPI.
This matters because the browser is unreliable: ad blockers, tracking prevention and closed tabs all lose browser-fired events. A server-to-server event does not depend on the visitor's browser still being open, or cooperating.
Match quality#
Facebook has to decide which person a conversion belongs to. The more identifying signal an event carries, the more often it succeeds, and the metric for this is Event Match Quality in Events Manager.
Two things raise it:
The _fbp and _fbc cookies. These exist only in the visitor's browser, so capturing them needs a page of yours with a tracking snippet on it. This is the main reason to use a landing page on Facebook traffic rather than sending clicks straight to the offer.
Advertiser parameters. adv1 through adv10 on a postback are forwarded into the CAPI event. If your offer source can pass back hashed contact details, they go here.
Check it arrived#
Events Manager shows received events within a few minutes. Fire a test conversion — the curl in conversions are missing — and watch for it there.
If the conversion is in PostbackX but not in Events Manager, the pixel is either not assigned to that campaign or its access token has expired. Tokens do expire, and the symptom is optimization quietly getting worse rather than an error, so it is worth checking when performance drifts for no other reason.