Duplicate conversions are one of the most damaging tracking problems precisely because they don't look like a problem. Inflated numbers feel like success, until you realise you've been optimising and spending against results that were never real.
How duplication happens
The most common cause is sending both a browser (pixel) event and a server (CAPI) event for the same conversion without deduplication. Both get counted. Other causes include tags firing on multiple triggers, thank-you pages that reload, and events firing on every step of a funnel.
Why it distorts decisions
If a channel's conversions are doubled, its ROAS looks twice as good as reality. Budget flows toward it. The 'winning' channel wins more spend, based on numbers that don't exist. Meanwhile genuinely strong channels get starved.
How to catch and fix it
Deduplication relies on consistent event IDs shared between browser and server events, so the platform recognises them as one conversion. Fixing it usually involves:
- Auditing where each event fires and how often
- Implementing shared event IDs across pixel and CAPI
- Removing duplicate triggers in Google Tag Manager
- Validating that one real conversion produces one recorded conversion
Related reading: our services and the Measurement Health Audit.
Think this might be happening in your account?
A Measurement Health Audit traces every conversion end to end and tells you exactly what's duplicated, missing, misfiring, or misaligned.