What is CAPI (Conversions API)? — Definition for DTC operators

Definition

CAPI (Conversions API) is a server-side API that sends conversion events from your backend directly to ad platforms like Meta and TikTok, bypassing the browser pixel. It is the workaround for iOS 14+ tracking restrictions that broke client-side conversion tracking.

How operators actually use it

Most DTC brands run CAPI alongside the browser pixel — pixel fires from the customer's browser, CAPI fires from Shopify or a backend webhook. Platforms deduplicate using an event ID. A correctly implemented CAPI typically recovers 15-30% of conversions that the pixel would have missed, improving Meta's optimization and lowering CAC by 10-20% on the same budget.

Common pitfalls and honest-cost notes

Bad CAPI implementations send orders without proper user-matching (email, phone, FBC, FBP), which Meta then cannot match to a user and the event is wasted. Worse: brands often send duplicate events without a matching event ID and Meta double-counts conversions, making ROAS look better than it is. Validate your CAPI in Meta Events Manager monthly and watch the event-match-quality score — anything below 7.0 is leaving performance on the table.

Related terms

Attribution — Attribution is the methodology used to credit revenue to marketing touchpoints — first-click, last-click, linear, time-decay, or data-driven multi-touch.
ROAS (Return on Ad Spend) — ROAS is revenue divided by ad spend, usually reported per platform (Meta ROAS, Google ROAS) and as a blended figure across all paid channels.
Incrementality — Incrementality measures how many orders or how much revenue a marketing channel actually caused, versus how many would have happened anyway.
Creative Fatigue — Creative fatigue is the decline in ad performance — falling CTR, rising CPM, falling ROAS — as the target audience sees the same creative repeatedly.
Ad Frequency — Ad frequency is the average number of times each unique user in your audience has seen a specific ad over a given window (typically 7 or 30 days).