What is a Conversions API?
A Conversions API (CAPI) is an ad platform's server-to-server connection for receiving conversion and event data, such as purchases, leads, and sign-ups, directly from an advertiser's server. It's the platform-specific endpoint that server-side tracking sends events to.
Meta's Conversions API is the best-known example, and other platforms offer their own versions, sometimes called an Events API. The shared purpose is the same: keep conversion data flowing when browser pixels can't.
How does a Conversions API work?
- An event happens. A customer buys, signs up, or takes another action on the advertiser's site or app.
- The server prepares it. The advertiser's server formats the event to the platform's specification, respecting consent settings.
- The API receives it. The event is sent to the platform's Conversions API over a secure server-to-server connection.
- The platform matches it. The platform connects the event to ad activity and, when a pixel also reports it, removes the duplicate.
What is an example of a Conversions API in use?
Keeping a campaign's signal strong
An online brand runs campaigns on several social platforms. As more shoppers block scripts, its pixels report fewer purchases each month, and the platforms' algorithms start optimizing on a shrinking sample.
After connecting each platform's Conversions API, the brand's server reports purchases directly, the platforms see a fuller picture of results, and campaign optimization has more to work with.
Conversions API vs. pixel
| Pixel | Conversions API | |
|---|---|---|
| Runs in | The visitor's browser | The advertiser's server |
| Blocked by browser limits and ad blockers | Often | Generally not |
| Who controls the data sent | The browser environment | The advertiser |
| Typical setup | A tag on the site | A server connection per platform |
| Best practice | Keep running | Run alongside the pixel, with deduplication |
Why does a Conversions API matter?
Ad platforms optimize toward the conversions they can see. When pixel data is incomplete, platforms learn from partial results, costs rise, and reporting undercounts what campaigns actually drove.
- Fuller conversion data. More conversions reach the platform, so optimization works from better signals.
- More reliable reporting. Results are less affected by browsers and blockers.
- One integration per platform. Each platform has its own API and format, which is why many teams use a managed service that handles them all.
How does Alli do this?
Alli by PMG's Audience Gateway sends first-party conversion events server-to-server to the ad platforms' conversion APIs, including Meta's Conversions API, TikTok's Events API, and Pinterest's Conversions API, each in the format that platform expects.
Audience Gateway captures each event once, distributes it to every connected platform, manages API changes for you, and feeds the same data into measurement in Alli, so there's one consistent record of conversions instead of a separate integration per platform.
Explore Alli Audience GatewayConversions API FAQ
What does CAPI stand for?
CAPI stands for Conversions API. It's the connection an ad platform provides so an advertiser's server can send conversion events directly, without relying on the browser.
Do I still need the pixel if I use a Conversions API?
Usually, yes. Platforms generally recommend running the pixel and the Conversions API together, with events matched so the same conversion isn't counted twice.
Is a Conversions API the same as server-side tracking?
Not exactly. Server-side tracking is the overall approach of sending events from your own server. A Conversions API is the receiving endpoint on a specific ad platform.
Which platforms offer a Conversions API?
Meta's Conversions API is the best-known. Other major platforms offer their own server-side APIs, under names such as Events API or Conversions API.
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