Set up Custom Conversions
When no standard event fits, you do not need a developer, you need a rule. A Custom Conversion is a filter in Events Manager that turns a slice of your Pixel or CAPI traffic into a named, optimizable event, matched on a URL pattern (such as 'URL contains /thank-you') or carved out of an existing event (such as 'Purchase WHERE value > $100'). It shows up as an optimization target in Ads Manager with no new code on the site.
Two creation modes
URL-based: no Pixel event code required; just match on the page URL. Operators are 'URL contains,' 'URL equals,' or 'URL doesn't contain.'
Event-based: filter an existing standard or custom event by parameter rules like `value`, `content_category`, or any other event parameter.
Use 'URL contains' over 'URL equals' for nearly every case. Exact match breaks on trailing slashes, UTM parameters, and protocol changes.
Categories and limits
Each Custom Conversion must be assigned a category: Add to Cart, Purchase, Lead, Subscribe, Complete Registration, or others. The category determines which reporting buckets it joins and what bidding optimization is available.
Hard limit: 100 active Custom Conversions per ad account. You can delete unused ones and create new ones, but you cannot exceed 100 simultaneously.
Common patterns
Instead of installing a Lead event on the thank-you page, create a URL-contains custom conversion on `/thank-you` and assign category Lead. This works for marketers without dev access.
You can assign a `value` rule (fixed dollar amount per fire) to a URL-based custom conversion to unlock ROAS reporting even when the underlying page has no Pixel value parameter.
Limits and restrictions
Single-page-app sites (React, Next.js) where the URL does not actually change on form submit will silently fail URL-based custom conversions. Fire a standard event in JavaScript instead.
September 2025: Meta restricts Custom Conversions whose names or URLs suggest specific health conditions or financial status. Flagged conversions are blocked from optimization.
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