What is a custom rule?
A custom rule applies an if-then condition to attribution data. It can standardize a source, medium, campaign, or channel before a report assigns conversion credit. For example, a team might group utm_source=Newsletter and utm_source=newsletter under one source name.
When is a rule useful?
Campaign names drift. Teams change tools, partners add redirects, and old links keep circulating. A rule can repair a known reporting pattern when the original tags cannot be changed retroactively. It can also create a business-specific channel grouping, such as separating paid brand search from other paid search.
A rule should follow evidence. If source=google and medium=referral appears in a report, first inspect the landing URL and referrer. Do not relabel every Google referral as organic search: a genuine referral or paid click may have a different cause.
How do you keep rules reliable?
- Name the source data pattern and the expected result.
- Test the rule on real touchpoints, including cases that should stay unchanged.
- Record when it takes effect and whether it changes historical reports.
- Check the output after campaign or tracking changes.
Rule order matters when more than one condition can match the same touchpoint. Keep narrow rules ahead of broad ones and document the precedence. A custom rule improves classification; it does not recreate a missing event or prove that the reclassified channel caused a conversion.
Use data discrepancy checks to spot unexpected shifts after a rule change.
Related terms: Attribution, Custom weight