Set up a Meta Custom Attribution Campaign

Once Meta's readiness indicator shows High (approximately 14 days after setup), you can run a Custom Attribution campaign. This is the Meta-side optimization layer — the step that actually puts Apex data to work in your ad delivery.

What you'll see in Events Manager

After Apex setup completes, a new Custom Attribution signal will appear under your Purchase event in Events Manager within 48 hours.

A few things to know about it:

• Isolated signal - The Custom Attribution signal is fully isolated from your standard Purchase event. Behind the scenes it is not even a Purchase event — it's an AppendAttribution event. You do not need to worry about deduplication with Elevar, your existing CAPI, or any other standard Meta events.
• No EMQ impact - This event does not affect Event Match Quality. EMQ is built for a different use case.
• Data quality issues will be surfaced in both Events Manager and Ads Manager. If they arise, Northbeam will work with Meta to resolve them.
• Export data. Events Manager has an export function that lets you download the raw signal Northbeam is sending at the ad-set level. Note: this may differ slightly from your Northbeam dashboard due to data delays.

Eligibility requirements

To use Custom Attribution in Ads Manager, your account must:

• Be running Sales-objective campaigns optimizing for Purchase events
• Use Highest volume or Highest value bid strategy (autobid only)
• Have at least ~50 Northbeam-attributed orders per day at the account level, based on your selected North Star settings, for best results. The technical minimum is 10 events in 7 days, but model performance improves significantly at higher volume.
  • For example, if your North Star is set to 1-day Clicks-Only, Blended Revenue, Accrual accounting, the account should have roughly 50 orders per day under that same Northbeam view.
• Have website or website + app as the conversion destination

Not compatible with: Value Rules, non-autobid bid strategies.

Campaign setup

In Ads Manager, create a new (or duplicate an existing) Sales-objective campaign. At the ad-set level, you'll configure:

1. Conversion location — Website (or Website + App)
2. Performance goal — Maximize number of conversions or Maximize ROAS
3. Dataset — select the pixel configured for Apex (it will show a green indicator when ready)
4. Conversion event — Purchase
5. Attribution model — select Custom
6. Custom attribution source — select the Custom Attribution Source (CAS) you would like to use for the ad set. Your CAS MUST match the pixel you are using for the ad set.

Custom Attribution is configured at the ad-set level — the same level as Incremental Attribution. The two are mutually exclusive on the same ad set, though both can exist within the same campaign.

Change one variable at a time. The only thing you're changing in this test is the attribution model. Keep everything else identical to your BAU setup:

• Performance goal — use whatever you normally run. Don't switch goals alongside Apex or the test won't be clean. Note: even if your primary KPI is ROAS, Maximize Conversions sometimes drives better ROAS in practice — stick with what you use today.
• Audience targeting — keep your existing inclusion, exclusion, and lookalike audiences. Setting "new customers" as your North Star in Northbeam does not automatically make Meta target new customers — you still need the appropriate exclusion audiences in the campaign itself.

Reporting

The Results column in Ads Manager for Custom Attribution campaigns reflects Northbeam-provided credit and value at the ad ID level — not Meta's standard attribution.

• Use Northbeam as your source of truth. Custom, Standard, and Incremental attribution in Ads Manager each use a completely different counting mechanism — comparing them there is apples-to-oranges. In Northbeam, they're all apples — always compare there.
• 48-hour reporting lag. Custom Attribution conversions appear in Northbeam immediately but show as – in Ads Manager for the first 48 hours. Use Compare Attribution Settings to view Meta standard attribution alongside Custom during that window.
• Don't compare against your account average. The channel average mixes campaigns at different stages, budgets, and optimization histories — it's a noisy baseline that will make results look worse than they are.

Running the A/B test

Use Meta's Conversion Lift experimentation tool to set up the test — not a manual campaign split. Meta uses the Conversion Lift harness behind the scenes to divide audiences cleanly and prevent cannibalization. Without it, you'll likely run into audience overlap that makes results unreliable.

Before setting up the Conversion Lift study, create your Custom Attribution campaign in Ads Manager first (following the campaign setup steps above). You'll assign that campaign to Cell 1 in the study. Your existing BAU campaign becomes Cell 2.

How to set up a Conversion Lift

1. Name your study clearly — e.g. "Custom Attribution vs BAU Q2 2026."
2. Create two cells — Cell 1 is your Custom Attribution test group, Cell 2 is your BAU group. Name them clearly (e.g. "Meta Custom Attribution — [Campaign Name]" and "Meta BAU — [Campaign Name]").
3. Assign campaigns to each cell — assign your Custom Attribution campaign to Cell 1 and your BAU campaign to Cell 2. Double-check this before moving on.
4. Set your conversion objective — select Purchases as the primary objective and choose the relevant dataset.
5. Set your schedule — start date one day before the campaign start date, end date one day after. This buffer ensures the full campaign flight is captured.
6. Set holdout size to the minimum allowed — for a standard two-cell study that's 2% total (1% per cell). You're splitting audiences here, not measuring lift in the traditional sense, so keep the holdout small to maximize your test group size.
7. Review the summary carefully before publishing. Publishing the study is what kicks everything off.

Test duration: Run for two weeks. One week is not enough to account for seasonality and variance.

In-Flight Best Practices:

• Avoid making changes to creative, audiences, or budgets mid-test. If changes are unavoidable, apply them to both cells simultaneously to maintain test integrity.
• Check for anomalies like duplicated events that could skew results.
• Avoid competing ads — similar ads outside the test that reach the same audience will pollute results.
• Keep campaigns in one cell only — the same campaign can't appear in multiple cells.
• Aim for at least $5K spend per cell and a 10K+ holdout for reliable results.

After a successful test: scaling

• Recommended: Run a 50/50 account-level A/B test to scale with confidence.
• Minimum: Move at least 20% of budget to Custom Attribution for at least two weeks before drawing conclusions.

Please reach out to your Customer Success Manager, Media Strategist, or Support if you have any questions.