How server-side conversions work for healthcare ads

What a browser pixel sends

An ad network’s pixel is a script that runs in the visitor’s browser. When it fires, the browser sends a request straight to the ad network. That request usually carries the address of the page, the page the visitor came from, the visitor’s IP address, browser details, and the network’s own cookies.

You don’t write that request. The pixel does. On a healthcare website, the page address alone can say a lot: a URL such as example.org/programs/alcohol-detox names a service.

What changes when the conversion is sent from a server

A server-side conversion is a request your server makes to the ad network’s conversion API after something happens on your site, such as a completed form. The visitor’s browser never talks to the ad network.

Because your server builds the request, you decide what goes in it. Anything you leave out never reaches the network.

// Sample conversion, sent from the server
{
  "click_id": "Cj0KCQ_sample_click_id",
  "event_code": "c_7f3a"
}

// removed before sending
page_url (removed)   referrer (removed)   ip_address (removed)   user_agent (removed)   email (removed)   phone (removed)

The click ID

When someone clicks an ad, the network adds an identifier to the landing page address. Google Ads uses gclid, Microsoft Advertising uses msclkid, and Meta uses fbclid. [VERIFY] That identifier means “this click, on this ad”. It doesn’t name the person or the page.

If the visitor opts in to advertising, the click ID can be kept in a first-party cookie for a limited time. When a conversion happens later, the server sends the click ID back to the network, and the network matches it to the original click.

The opaque event code

The network also needs to know which conversion happened. Instead of a name like “insurance verification for detox”, Conversion Relay sends a code such as c_7f3a. The code means something in your own dashboard and nothing to the network.

What the network does not receive

With Conversion Relay, the request carries only the network click ID and an opaque event code. The page address, referrer, IP address, browser details, and anything the visitor typed stay behind. Each network’s API has its own required fields; the integration pages list what is sent to each one. [VERIFY]

Consent still comes first

Server-side reporting doesn’t replace consent. On a site running Consent Gateway, no script loads and no click ID is kept until the visitor opts in. If they say no, there is nothing to report.

What you give up

A pixel can tell an ad network much more than a click ID can, and some networks use that extra data to model conversions they can’t match. Expect fewer matched conversions than a pixel reports. What you get in exchange is a request you can read line by line.