Comparison

A comparison is a temporary filter you apply to a standard report to view two or more subsets of data side by side, split by a condition.

You add a comparison from the top of most reports by choosing a dimension and the values to include, for example device category is mobile versus device category is desktop. GA4 then draws each subset as its own line and row so you can read them against each other. You can stack several comparisons and save the useful ones for reuse.

You open Traffic acquisition and add one comparison for new users and another for returning users. The report now shows both cohorts in parallel, and you can see paid search brings volume from new users while returning users arrive mostly direct.

Comparisons are report-level filters, not segments. They live in standard reports, they do not carry the user, session, or event scope that segments do, and they cannot do sequence or exclusion logic. When you need that, move the same question into an exploration and build a real segment. Treating a comparison as a segment is where the analysis quietly gets shallow.

Good for a fast split in a fixed report. Not a substitute for a segment.