Meta Conversions API Explained: Setup, Deduplication and Match Quality

If you run Facebook and Instagram ads, the Meta Pixel alone no longer gives Meta the full picture. Browser restrictions and ad blockers stop some events from reaching Meta. The Conversions API (CAPI) sends the same events from a server, so Meta receives them even when the browser does not.

Pixel and Conversions API work together

The recommended setup is not to replace the Pixel. It is to run both. The Pixel sends events from the browser, CAPI sends the same events from the server, and Meta combines them.

Deduplication: the part most setups get wrong

When the same purchase is sent twice, once by the Pixel and once by CAPI, Meta needs a way to know it is one event. That is done with two matching values:

• event_name must be the same in both, for example Purchase.
• event_id must be the same in both, for example the order ID or a unique ID generated on the page.

If the event IDs do not match, conversions are counted twice and your reported ROAS looks better than it really is.

Event Match Quality

Meta scores how well it can match your server events to real people. This is called Event Match Quality. You improve it by sending more customer information parameters, hashed where required:

• Email and phone number (hashed)
• First name, last name, city, postal code and country (hashed)
• The fbp and fbc cookie values
• Client IP address and user agent
• External ID, such as your customer ID

Ways to set it up

• Platform integrations for Shopify, WooCommerce and others. Quick, but with limited control.
• Server-side Google Tag Manager with a Conversions API tag. Flexible, and it works with your GA4 and Google Ads setup too.
• Direct API integration built by a developer.

How to check it is working

• Use the Test Events tool in Meta Events Manager.
• Check that events show both Browser and Server as sources.
• Confirm deduplication is happening and there are no duplicate warnings.
• Watch Event Match Quality for your key events, especially Purchase and Lead.

Need a hand with this?

If you are not sure your setup is sending the right data, request a free tracking audit. I will review your tags, events and conversion actions and send you a clear list of what to fix.