What type of metric reports the number of unique datapoints in Datadog?

The type of metric that reports the number of unique datapoints in Datadog is a set. Sets are designed to collect a unique series of values within a specified time frame and are particularly useful for tracking unique occurrences, like user IDs or any distinct identifiers.

Unlike other metric types, which focus on values over time or aggregated statistics, sets allow you to count how many unique items appear in a given dataset. This characteristic makes it particularly beneficial for scenarios where understanding the diversity of data points—rather than their individual numerical values—is critical.

While gauges measure the current value of a metric at any given time, distributions and histograms summarize data across predefined buckets, focusing on frequency rather than uniqueness. Hence, in the context of tracking unique data points, the set metric type is the most appropriate choice in Datadog.