How to set up Facebook event deduplication in Google tag manager

This is the click-by-click version of server-side tracking event deduplication, for Meta only. It assumes you already have a Meta pixel tag in the web container and a Meta Conversions API tag in the server container. If not, start with how to set up the Facebook Conversions API.

Step 1: create the ID in the data layer

When the event happens, push it with an ID. For a purchase use the order number:

dataLayer.push({
  event: "purchase",
  event_id: "ord_10293",
  ecommerce: { transaction_id: "10293", value: 59.9, currency: "USD", items: [] }
});

For events without a natural ID, create a random one, for example from a timestamp and a random number, once per event.

Data in, clean out

Raw events in. Clean events out.

Open Tracked collects each event on your own domain, removes the noise and sends what is left to Meta, Google Ads, TikTok.

cookie expiredad blockermissing click IDlate event

MetamatchedGoogle AdsdedupedTikToksentYour reportclean

Step 2: read it in the web container

Step 3: read it in the server container

The short version

3 things to remember

Scroll and the points stack up.

01

Push an event_id into the data layer with the event.

02

In the web container, put it in the Meta pixel tag as the event ID. In the server container, read it from the event data and send

03

Use the same event name on both sides, then confirm in Test Events.

Step 4: test

1. Open Meta Events Manager, then Test Events, and use your test code.
2. Place a test order.
3. You should see two lines for the purchase, from Browser and Server, each with the same Event ID.
4. Open the details: Meta marks one as deduplicated.
5. Remove the test event code from the server tag before you go live.

When Meta still counts twice

Where this fits in the bigger set-up

Deduplication is one part of a working Conversions API set-up. The others are matching data (see event match quality), cookies that survive Safari (see Safari ITP) and consent (see Consent Mode v2). If purchases are doubled, fix the event ID first, because every other measurement depends on counting each order once. A week of clean data after the fix will tell you whether the other parts need work. Keep a note of where the event ID is created and which tags read it, so the next person who edits the checkout does not break the link by accident.

Terms you will see

Data layer

A list on the page where you push values for Tag Manager to read.

Data Layer Variable

A Tag Manager variable that reads one value from the data layer.

Event data

The parameters of an event inside a server container.

Test event code

A code that sends events to the Test Events tab only.

Deduplication

Counting the browser and server copy of an event once.

Platform-specific checks

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Frequently asked questions

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Written by

The Open Tracked team

We build Open Tracked: server-side tracking hosting, analytics and the tools around them, for stores that spend on ads. Questions about this guide, or an idea for the next one?

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