Why stores are using Facebook’s Conversions API

Buyer Personas for Facebook Ads

Over three million businesses worldwide use Facebook Ads.

Their massive reach ensures they play a part in every ecommerce store’s marketing strategy. Of course, the key to a successful Facebook Ads strategy comes down to creating ads and targeting audiences based on good data.

If you want to measure the return on investment from your Facebook Ads accurately, you need to share page-view and conversion events with Facebook. In the past, Facebook recommended you add Facebook Pixel onto all your web pages to enable this event tracking, which triggers a ping to Facebook’s servers. Originally this ping was in a request for a single white pixel loaded at the bottom of the page (hence ‘Pixel’), but nowadays the ping is usually sent from Facebook’s Javascript.

In this post we’ll explain:

  • Why you need to set up Conversions API today to improve your marketing
  • How this extra tracking opens up more advertising options
  • How you can implement the Conversions API on a Shopify store

What’s wrong with Facebook Pixel?

Over the 10 years since Pixel’s launch, three big trends have reduced its effectiveness at tracking return on Facebook Ad spend:

  1. Usage of ad blockers to stop third-party scripts from known advertising platforms (like Facebook) from sending a ping
  2. Browsers (e.g. Safari’s ITP) restricting what third-party scripts and cookies can track
  3. The increasing share of clicks from Facebook’s mobile app, exacerbating the 2nd trend

The introduction of GDPR and similar regulation requiring that customers opt into being tracked in their web browser presents the latest obstacle, and perhaps the biggest yet.

The combined effect is that a smaller percentage of Facebook users who click on your ad can be tracked on subsequent web sessions. So a smaller percentage of the purchases which resulted from Facebook Ads can be attributed to Facebook.

Tip: Want to dig deeper into the challenges of measuring ROI from Facebook? See our recent webinar.

Why did Facebook launch Conversions API?

The lack of marketing attribution is a big problem for Facebook, as it makes their Ads look relatively less effective and more expensive than other channels.

To combat these trends Facebook launched the Conversions API (CAPI) in 2020, and in 2021 expanded it to enable tracking of any event (not just the purchase) directly on Facebook’s servers.

In contrast to Pixel, Facebook Conversions API is a server-to-server data connection, allowing events linked to a visitor from Facebook to be sent independent of the browser sessions.

What’s the advantage of CAPI over Pixel?

Firstly, the server-side events are not sent from the customer’s browser, so they are not interrupted by the web browsing and privacy trends mentioned above. Close to 100% of the purchases from your store can be shared with Facebook via CAPI.

Secondly, even if the customer has opted out of marketing cookies — meaning the purchase cannot be attributed via Facebook’s Pixel ID — CAPI can send some extra user identifiers like email address, physical address and phone number. These give Facebook a better chance of linking the purchase to a user, and from there to the Ad the user clicked on. See more on user data below.

This personally identifiable data is sent securely from Shopify to Facebook via a SSL connection, so there is no risk of security leaks.

Conversions API also gives stores the ability to link delayed conversions back to the original ad campaign. A good example is subscription commerce (see Facebook’s case study), where stores need to see the 2nd or 3rd purchase to evaluate if the Facebook campaign is effective.

Tip: Littledata’s connectors capture recurring payments from the Shopify checkout automatically.

Using CAPI might not fix all your attribution issues, but one agency reported a 25% to 35% boost in attribution for Shopify stores using this technique. If you are a big Facebook spender, even a 20% improvement in attribution might be worth thousands of dollars of implementation costs.

How should I use CAPI on my Shopify store?

Facebook recommends you use a partner integration work with CAPI, and there are three ways to integrate Conversions API with your Shopify store:

  1. Shopify’s inbuilt Facebook channel
  2. Server-side Google Tag Manager (sGTM)
  3. Littledata + Segment

To help you decide which is right for you, here is a quick comparison table.

Integration routeCAPI used forSupports all FB account and campaign setupsComplexity of setupCost of maintenance
Shopify’s Facebook channelJust conversionsNoLow Low
sGTMAll events triggered in GTMYesHighHigh
Littledata + SegmentAll server-side events from LittledataYesLowLow

You might be alright using Shopify’s Facebook channel if your campaign structure is simple, uses just one Facebook account, and you only target based on first-time purchases. Otherwise you should look at Segment’s Facebook CAPI destination or sGTM.

sGTM is a version of Google Tag Manager where a trigger on the browser (e.g. the customer viewing a checkout step) is passed on to a dedicated cloud server, where the GTM container logic decides which events to trigger. So it’s a hybrid of client and server side tracking.

Tip: Learn how to use server-side tracking to improve customer loyalty and lifetime value.

What are the limitations of using sGTM?

You might have been told server-side GTM (sGTM) is the best way to work with CAPI. I disagree.

Firstly, you have a complex setup to get all the events triggered from the browser in a way that the GTM server can handle. An analytics agency will typically charge you a few thousand dollars to get this working.

Then you have to spin up your own GTM server in Google Cloud. That’s not a big cost – probably a few hundred dollars a month – but it is a maintenance headache. Who is going to check the server is up and running as expected?

There are some limitations of where you can add the GTM container on the Shopify storefront. Unless you are using Shopify Plus, you can’t add to the checkout pages – so you can’t capture the checkout steps in the example above.

Finally, you have to consider all the many changes Facebook makes to its APIs every year. Typically there is an update every few months that whoever maintains the GTM container would need to work with. With the other integration options this is included in the subscription fee.

Yes, sGTM is flexible and will allow you to send similar event data to other destinations – but that’s also something that Segment does at no additional cost.

Server-side tracking for Shopify stores

Littledata’s solution is to send comprehensive event data from Shopify to Segment, and include event properties that are compatible with Segment’s Facebook CAPI destination.

The setup is as easy as:

  1. Create a workspace on Segment.com
  2. Install Littledata’s Shopify app for Segment
  3. Configure Segment’s Facebook destination

What this brings you – in addition to the purchase event sent from Shopify’s integration – is complete server-side tracking of Add to Cart and Checkout Step events to Facebook, all linked back to the users on Facebook. These extra events can be used to target users who abandon cart or checkout.

You can use Segment’s Facebook audience sync to build even more powerful retargeting audiences – e.g. a lookalike audience of your most valuable customers.

Things to note on custom user information

Sending the Facebook events direct from server to server allows Littledata to add a number of customer user identifiers, so Facebook can better match the event to which Ad was clicked on.

User properties that are automatically mapped to Facebook include:

  • Email
  • Phone number
  • City state
  • ZIP
  • Country
  • Client IP address
  • Click ID (fbc)
  • Browser ID (fbp)

You can control which properties are passed on to Facebook in Segment Protocols, so better manage customer privacy choices.


If Facebook Ads is an important part of your store’s marketing strategy then Facebook CAPI is an essential tool to start using. The trends that make it more reliable that Facebook Pixel are ongoing, so if you don’t think you need it now you may well need it in a few months time.

Your options to integrate Facebook on a Shopify store include Shopify’s in-built Facebook channel and server-side GTM, but we recommend using Littledata’s Shopify source plus Segment’s Facebook destination for quick setup and easy maintenance.

Then you can get:

  • More accurate attribution of Ads
  • Better retargeting for abandoned carts
  • Better audience matching in Facebook.

Give it a try and see what better results you can achieve!

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