Guide 65 · Reports · GA4 + Tag Manager
Build a segment overlap exploration: how much your audiences actually share
A segment overlap exploration draws up to three segments as a Venn diagram and counts the users in each overlap. It answers whether two audiences are really two audiences.
After step 5, the Venn diagram shows each segment's size, the overlap counts, and the share of each segment that also belongs to the first.
Download the report reference: the Segment overlap reference (JSON) (1124 bytes, MD5 9cd380fca18e7e16abf7ba71e0f86607). It holds the report or exploration definition and the worked example with the recomputed figures shown on this page.
What you need
- Viewer access or above on the property to build.
- The entry point: Explore in the left navigation, then the segment overlap template.
- Two or three segments defined in advance — for example, purchasers, email subscribers, and mobile users. An overlap of undefined segments is a guess.
The trace
- Open Explore and pick the segment overlap template. Click Explore in the left navigation, then create a blank exploration and change the technique to Segment overlap, or pick the template. The canvas shows a Venn diagram.
- Build the segments first if they do not exist. In the Variables panel, click the add icon beside Segments and define each segment — a user segment for people, a session segment for visits, or an event segment for actions. Segments are subsets of users, sessions, or events that match conditions you set.
- Add up to three segments to the canvas. Drag each segment from Variables into Tab Settings, or double-click it. Segment overlap supports up to three segments at once; a fourth cannot be added.
- Read the overlap counts, not just the picture. The diagram shows each segment's size and the count in each overlap region. Divide an overlap count by its segment size for the overlap share — the worked example below does that division for three segments. A 70% overlap means the two segments are mostly the same people.
- Save it under the question it answered. Save the exploration with a name that states the comparison, for example, Purchasers versus email subscribers overlap. You can also build a new segment from an overlap region and export it as an audience.
Dead ends
DEAD END — OVERLAPPING SEGMENTS BUILT FROM THE SAME CONDITION. Two segments defined by nearly the same condition will overlap almost fully. That result measures your definitions, not your users.
DEAD END — ADDING A FOURTH SEGMENT. Segment overlap takes up to three segments. A fourth cannot be added; split the question into two explorations instead.
DEAD END — READING THE DIAGRAM SHAPE INSTEAD OF THE COUNTS. The diagram's circles are drawn for readability, not to scale. The counts and the overlap shares are the answer; the picture is the index.
End state
A segment overlap exploration turns a hunch about two audiences into counts. The worked example below recomputes the overlap share for three segments, so a large-looking overlap can be checked against its numbers.
Worked example — stated inputs, recomputed results. The segment sizes below are stated inputs for the example. Overlap share is the overlap count divided by the segment size.
| Segment | Users | Also in the first segment | Overlap share |
|---|---|---|---|
| Purchasers | 1,240 | 1,240 | 100.0% |
| Email subscribers | 2,860 | 868 | 30.3% |
| Mobile users | 3,420 | 744 | 21.8% |
Sources
- Analytics Help — Get started with Explorations — segment overlap shows how different user segments relate to each other and can identify new segments; up to 10 segments per exploration
- Analytics Help — Confirm that you are collecting data — many reports and explorations can take 24 to 48 hours to process data
Checked 11 November 2026. The click paths above are the ones in Google's help pages, opened or read 11 November 2026 (the Explorations and detail-report pages were opened in full; the report, library, navigation and thresholds pages were read from Google's help results the same day, after the browser hit a rate limit). No step in this guide was run inside a live Analytics property, because that needs a Google sign-in and this site does not sign in as anyone. The worked-example figures on this page were recomputed in Python with decimal arithmetic, and the downloadable JSON file carries the same recomputed figures. Google moves menu items without warning; if a path on this page no longer matches, the linked help page is the current map.