If you run Facebook or Instagram ads and someone has mentioned "CAPI" or "the Conversions API" to you, this is what they mean and why it matters to the money you spend.
The pixel sees less than it used to
The Meta Pixel is a piece of code on your website. When someone buys, enquires or adds to basket, it tells Meta. Meta uses that to work out who to show your ads to next and to report what the ads produced.
The problem is that the pixel lives in the browser, and browsers have become much better at blocking it. Since Apple's iOS 14 changes, ad blockers and stricter cookie settings, a meaningful share of the people who buy from you are invisible to the pixel. Meta then optimises on a partial picture and your reports under-count what the ads did.
What the Conversions API does
The Conversions API sends the same events from your server (or your website platform) straight to Meta, rather than relying on the visitor's browser. Shopify, WooCommerce and most modern platforms can do this natively; for anything custom it's set up through Google Tag Manager's server-side container or a connector.
Run alongside the pixel, with the events deduplicated so the same purchase isn't counted twice, it gives Meta a fuller set of real sales to learn from. On the Cheezious account in 2023, setting up purchase tracking was what made sales campaigns possible in the first place; once they ran, the account averaged a 36.88 ROAS and the best ad sets came in 76% below Meta's peer benchmark on cost per purchase.
Four questions to ask whoever built your site
- Is the Conversions API set up, and is it sending purchases or leads, not just page views? Events Manager shows which events arrive from the browser and which from the server.
- Are the browser and server events deduplicated? Each event needs a shared event ID. Without it your purchases double-count and your ROAS is flattered.
- What is the event match quality score? Meta rates each event out of 10 on how well it can match the customer. Below 6 usually means customer details such as email and phone aren't being sent.
- Which event is set as the priority? If "view content" ranks above "purchase", you're optimising for window shoppers.
What it costs
Nothing to Meta. The cost is the set-up time, which is a few hours on a standard Shopify or WordPress store and more for a custom site. It's the first thing I check on any account I take on, and I'd rather fix it before a pound is spent than explain a bad month afterwards.
If you'd like a second opinion on your own set-up, the tracking page has a six-question check you can run in a minute.
I run paid ads on Meta, Google and TikTok across the UK, the Gulf and Pakistan, and build the tracking and pages around them. Get in touch or find me on LinkedIn.