Custom Conversion
Custom conversion explained — a rule that classifies received activity into a conversion definition for reporting and, where supported, optimization.
Updated July 22, 2026.
A custom conversion is a rule layered on top of event or page data to identify a narrower conversion, often using URL, event name or parameters.
Why it matters
Custom conversions let advertisers split one received event into business-specific outcomes without changing every source event. They are useful for product categories, high-value orders, particular forms or lifecycle subsets—but can duplicate the underlying event if campaign and reporting settings are not governed.
How it works across ad platforms
| Platform or system | Current treatment |
|---|---|
| Meta | Custom conversions classify eligible dataset activity by event/URL/parameters. |
| Google Ads | Creates conversion actions and URL/manual rules rather than Meta-style custom conversions. |
| Creates source-specific conversion rules. | |
| Microsoft Advertising | Creates UET conversion goals with event matching conditions. |
| TikTok | Uses standard/custom events and event configuration; custom event is not the same as a Meta custom conversion. |
| Uses standard/custom conversion events. | |
| Uses configured event types and custom event. |
Implementation rules
- Use a custom conversion for a stable, meaningful subset.
- Name the rule by business outcome, not implementation detail.
- Define whether the base event and custom conversion can both appear in optimization/reporting.
- Use parameters that are consistently populated.
- Record rule changes with effective dates.
Common mistakes
- Assuming every platform uses Meta’s custom-conversion model.
- Creating overlapping rules that count the same event multiple times.
- Basing a rule on a URL containing personal information.
- Using a parameter that is absent on some events.
Minimum QA
- Send qualifying and non-qualifying test events.
- Confirm only the intended subset is classified.
- Review campaign selection.
- Reconcile custom conversion totals with base events.
Official sources
- Meta Pixel setup
- Meta Conversions API
- Google Ads conversion setup
- LinkedIn conversion setup
- Microsoft conversion goal types
- TikTok standard events
- Reddit Conversion Events
- Pinterest conversion events
Technically verified: July 22, 2026. This reference uses official platform sources only for platform-specific behavior. Definitions and implementation recommendations are editorial synthesis by The Ad Spend.