(not set) appears in Google Analytics reports when a dimension has no value for some rows. It is not an error message by itself, but a high share of (not set) is a sign that data is missing or collected in an unexpected order. The cause depends on which dimension shows it, so the fix starts with identifying the report.
Common causes by dimension
Each dimension has its own typical reasons.
- Landing page: a session started with an event other than page_view, often after a session timeout
- Source or medium: events sent without session context, such as Measurement Protocol hits or events before the tag initialized
- Campaign: traffic without UTM parameters or ad platform auto-tagging
- Custom dimension: the parameter was not sent with that event, or was sent before registration
- Country or city: location could not be determined from the request
How to investigate
Start with the size of the problem: a small share is normal. Then add secondary dimensions such as event name, device or browser to the (not set) rows to see what they have in common. Check Google Tag Manager's preview mode to confirm which events fire first on page load.
Consent setups can contribute. If analytics storage is denied until a user acts on the banner, early events may arrive without the context they would normally have.
When to leave it
Some (not set) is a permanent feature of event-based analytics. Focus on cases where it hides something you need, such as the landing pages that start key-event sessions.
Example
Tracing landing page (not set)
Suppose Wickerline, a support desk SaaS, sees (not set) as its fourth-largest landing page. The rows are mostly from the app's documentation, where people leave tabs open for hours and come back with a click. Those clicks start new sessions without a page_view. The team accepts it for docs and checks that marketing pages show only a trace.
Common mistakes
Filtering it out of every report
Hiding (not set) hides the symptom. Investigate first, then decide whether to exclude it.
Confusing it with (not provided)
(not provided) is about hidden search keywords. (not set) is a missing value in any dimension.
Questions
Yes. If key events are recorded in sessions with no source or landing page, they cannot be credited to the right channel or page.
