The essentials
- Definition: the conversions API (CAPI) sends conversion events from the site's server to the advertising platform, alongside or instead of the pixel installed in the browser.
- Why: ad blockers, browser restrictions and consent refusals lose 20 to 40% of the events sent by the pixel alone.
- 2026 gains: 10 to 30% more attributed conversions and a more accurate cost per result, provided deduplication is correct.
- Watch out: every event must carry a unique identifier shared between pixel and server, otherwise conversions are counted twice.
Theconversions API (often shortened to CAPI) is a mechanism through which a site sends conversion events from its own server to an advertising platform, instead of relying solely on the script installed in the visitor's browser. Meta popularised it under that name in 2020; the equivalent exists at TikTok, LinkedIn, Pinterest and Snapchat, and at Google in the form of server-side tracking and enhanced conversions. The principle is the same: move measurement out of the browser, which has become unreliable, and into the server, which is less so.
Why the browser pixel is no longer enough
| Obstacle | Effect on the pixel | Share of traffic affected |
|---|---|---|
| Ad blockers | The script doesn't load | 20 to 35% in France depending on the audience |
| Browser protections (Safari, Firefox) | Cookies limited to 7 days, or blocked | Around 35% of mobile traffic |
| Consent refusal | The pixel doesn't fire | 25 to 40% of visitors |
| Apps and private browsing | Partial or absent tracking | Variable |
| An unstable connection, a page left too quickly | Event lost | A few percent |
Taken together, these obstacles cost a site relying on the pixel alone 20 to 40% of its conversions. The advertising algorithm then optimises against a partial reality and underestimates the campaigns reaching the most protected audiences.
What the conversions API brings
- More complete events: sending from the server escapes ad blockers and browser limits; the gains observed run from 10 to 30% more attributed conversions.
- Offline conversions: a sale signed over the phone or in store can be sent back to the platform, which the pixel cannot do.
- Better matching: the data sent (hashed email, phone, order ID) improves matching with advertising accounts, and therefore the accuracy of attribution.
- Fairer optimisation: with more complete data feeding automated bidding, cost per result falls mechanically by a few points; see Smart Bidding.
- Less dependence on the browser: future changes to browser protections affect measurement less; it is the logical sequel to the end of third-party cookies.
Setting up the conversions API
- Choose the integration method: your CMS's official extension (Shopify, WooCommerce, PrestaShop), a Google Tag Manager server container, a partner platform, or direct development against the API.
- Send the same events as the pixel: purchase, add to basket, form, with the same parameters and the monetary value.
- Pass the matching data: hashed email and phone, the ad click identifier, IP address, user agent — within the bounds of consent.
- Deduplicate: every event carries a unique identifier sent identically by the pixel and by the server, so the platform recognises one and the same event.
- Respect consent: sending from the server does not exempt you from consent; it must be conditioned on the signals from your CMP.
- Verify: the platforms' diagnostic tools show the quality of the matching and flag duplicates; the Meta setup is covered in detail in the Meta pixel.
Deduplication, the point where installations fail
When both the pixel and the server send a purchase with no shared identifier, the platform counts two conversions. The ROAS on display doubles, bidding runs away, and budget decisions become wrong. The rule is simple: generate one unique identifier per event, pass it to both the pixel and the server, and check in Events Manager that the deduplication rate is close to 100%. A sudden gap between the conversions the platform reports and those in GA4 or your e-commerce platform is the first symptom of a deduplication problem.
How GreenRed helps
Rather than juggling several tools, GreenRed's SMO and SMA social media tracking brings these metrics together in a single dashboard, compares them over time and tells you which actions come first. You can try it free, with no card, from the Pricing.
Frequently asked questions
What is the conversions API (CAPI)?
A mechanism that sends conversion events from the site's server to the advertising platform, alongside the pixel installed in the browser. It exists at Meta, TikTok, LinkedIn and Pinterest, and in other forms at Google, to recover the conversions the browser no longer passes on.
How many conversions does the conversions API recover?
Between 10 and 30% more attributed conversions depending on the audience and the sector, bearing in mind that the pixel alone loses 20 to 40% of events to ad blockers, browser protections and consent refusals.
Should you keep the pixel if you install the conversions API?
Yes — the two complement each other: the pixel captures the browser's signals, the server fills in what is missing. The condition is deduplication, meaning one unique identifier per event sent identically by both channels, without which conversions are counted twice.
Does the conversions API exempt you from consent?
No. Sending from the server is still processing personal data for advertising purposes: it must be conditioned on the consent collected by your CMP. Technically invisible to the visitor, it is nonetheless subject to the same obligations as the pixel.