Conversion API

What is a conversion API?

A conversion API (CAPI) is a server-to-server integration that lets businesses send purchase, lead, and other conversion events directly from their backend to an advertising platform's servers. Instead of relying on a browser-based pixel to detect when a conversion occurs, the event data is transmitted via an authenticated API call from the advertiser's server infrastructure.

Major ad platforms each offer their own conversion API: Meta's Conversions API (formerly Facebook CAPI), Google Ads API (enhanced conversions), TikTok Events API, Snapchat Conversions API, and Pinterest API for Conversions. While the implementation details differ, the core concept is the same — deliver conversion data through a reliable server-side channel.

Why it matters

Conversion APIs exist because browser-based conversion pixels are failing at an accelerating rate. When a customer clicks an ad, visits a site, and completes a purchase, the pixel on the confirmation page must fire successfully for the ad platform to register the conversion. That chain breaks more often than most marketers realize:

• Ad blockers — Block the pixel script entirely, making the conversion invisible to the ad platform.
• Browser restrictions — ITP, ETP, and cookie deprecation prevent the pixel from matching the conversion back to the original ad click.
• Page abandonment — If the user closes the tab before the confirmation page fully loads, the pixel never fires.
• Mobile app switches — Cross-app navigation on mobile devices frequently breaks pixel tracking continuity.

When conversions go unreported, ad platforms lose optimization signals. Campaign algorithms cannot learn which audiences and creatives drive results, leading to higher CPAs, worse targeting, and wasted spend. Conversion APIs restore this signal by providing a direct, reliable data path.

How it works

A conversion API integration typically follows this flow:

1. Event capture — The server records a conversion event (purchase, sign-up, add-to-cart) in its application logic, along with relevant metadata: transaction value, currency, product IDs, and user identifiers.
2. Identity matching — The server includes identity parameters that help the ad platform match the event to a user: hashed email, hashed phone number, click ID (fbclid, gclid, ttclid), IP address, and user agent.
3. API transmission — The server sends an HTTPS POST request to the platform's conversion endpoint with the event payload, authenticated via an access token or API key.
4. Deduplication — If both a pixel and the conversion API report the same event, the platform deduplicates using an event ID, ensuring the conversion is counted once.

Key considerations

Implementing conversion APIs effectively requires attention to several factors:

• Event deduplication — Running both pixel and CAPI in parallel (recommended by most platforms) requires consistent event IDs to prevent double-counting. Without proper deduplication, reported conversions inflate and attribution models distort.
• Data freshness — Most platforms accept events up to 72 hours after they occur, but real-time or near-real-time delivery produces better optimization signals.
• Match quality — The more identity parameters included in each event, the higher the platform's match rate. Meta reports that including hashed email, phone, and click ID together yields match rates above 90%.
• Consent compliance — Server-side transmission does not exempt businesses from consent requirements. Events must still respect user opt-out preferences, and PII must be hashed before transmission.

How Ingest Labs handles conversion APIs

Ingest Labs connects to 20+ conversion APIs out of the box — including Meta Conversions API, Google Ads, TikTok Events API, and Snapchat — through pre-built destination connectors that require no custom server code. Ingest ID's identity resolution enriches each event with durable first-party identifiers and click IDs, achieving 95% attribution accuracy while automatically handling deduplication, payload formatting, and consent filtering for each platform.