The Conversions API is a server-to-server connection between your website or store platform and Meta. When an order is placed, your server tells Meta directly, instead of relying only on the Meta Pixel running in the shopper's browser.
Why it matters
Browser tracking has become less reliable. Ad blockers stop the pixel loading, browsers restrict cookies, and Apple's privacy changes limit tracking on iPhones and in Safari. Every missed Purchase is a sale Meta can't learn from, so optimisation weakens and your reported ROAS looks lower than reality.
Server events aren't affected by those browser-level blocks, so the Conversions API fills many of the gaps. It doesn't bypass consent, though: only send data you're allowed to share under your privacy notice. And it improves what Meta receives rather than guaranteeing better results. Its value shows up as more complete reporting and more signal for optimisation.
Deduplication: the part people get wrong
Most stores send each event twice, once from the browser and once from the server. Meta counts it once only when both copies carry the same event name and the same event ID (eventID in the pixel code, event_id in the server payload) and arrive within Meta's deduplication window, which is 48 hours at the time of writing. Use something unique per action, such as the order number for Purchase.
If IDs are missing or don't match, Meta counts both copies and your conversions are double-counted.
What a good server event includes
- event_name, event_time and event_id.
- action_source set to website, plus the URL where the event happened.
- Customer information: hashed email and phone, an external ID, the browser's fbp and fbc values, the IP address and the user agent. More matched details mean a better event match quality score.
- custom_data: value, currency and content IDs for purchases.
How to set it up
- Start with your platform's integration. Shopify and most major e-commerce platforms offer a combined pixel and Conversions API setup. Choose the highest data-sharing level your consent setup allows.
- Otherwise pick a method: Meta's Conversions API Gateway, server-side Google Tag Manager, or a direct integration built by your developer.
- Test with the Test events tool in Events Manager, then review the deduplication and event match quality diagnostics.
- Monitor weekly. Server events can fail silently after a platform or app update.
Our Shopify setup checklist walks through each step, including how to confirm deduplication.
Frequently asked questions
Do I need both the Meta Pixel and Conversions API?
For most websites, yes. Meta recommends a redundant setup in which the pixel and Conversions API send the same events with matching event IDs, so Meta can deduplicate them. The pixel captures browser signals and the server catches events the browser misses.
What is the difference between the Meta Pixel and Conversions API?
The pixel runs in the visitor's browser and sends events from there. The Conversions API sends events from your server directly to Meta. Browser tracking can be blocked or limited while server events are more dependable, so the two work best together.
Why are my Purchase events being double-counted?
Usually because the browser and server events don't share the same event name and event ID, so Meta can't tell they're the same purchase. Pass a unique ID, such as the order number, in both. Also check you don't have two pixel installations firing Purchase.
