This article is about Google Analytics 4 properties. Refer to the Universal Analytics section if you're still using a Universal Analytics property, which will stop processing data on July 1, 2023 (July 1, 2024 for Analytics 360 properties).

[GA4] Cardinality

Cardinality refers to the number of unique values assigned to a dimension.

Some dimensions have a fixed number of unique values. For example, the Device dimension can have up to 3 values — desktop, tablet, mobile. In this example, the cardinality of Device is 3.

Other dimensions, like the Item ID, Page path, or Page location dimension, can have more possible unique values. Websites and apps in the ecommerce space could have hundreds of thousands of items. Websites could have hundreds of thousands of unique pages. These dimensions would be expected to be high cardinality.

High-cardinality dimensions

High-cardinality dimensions are dimensions with more than 500 unique values in one day. High-cardinality dimensions increase the number of rows in a report, making it more likely that a report hits its row limit, causing any data past the limit to be condensed into the (other) row.

You should only use high cardinality dimensions when the information collected is necessary for the business, as they can more quickly cause reports to reach the row limit.

Note: Google Analytics 4 does not have a cardinality limit on an individual dimension. Properties can have dimensions with any number of values, but when using high-cardinality dimensions, be sure to review best practices on custom dimension setup and best practices on how to avoid the other row.
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