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Metric

A metric is a set of user experience data for a single web performance metric, like "first contentful paint". It contains a summary histogram of real world Chrome usage as a series of bins.

JSON representation
{
  "histogram": [
    {
      object (Bin)
    }
  ],
  "percentiles": {
    object (Percentiles)
  }
}
Fields
histogram[]

object (Bin)

The histogram of user experiences for a metric. The histogram will have at least one bin and the densities of all bins will add up to ~1.

percentiles

object (Percentiles)

Common useful percentiles of the Metric. The value type for the percentiles will be the same as the value types given for the Histogram bins.

Bin

A bin is a discrete portion of data spanning from start to end, or if no end is given, then from start to +inf.

A bin's start and end values are given in the value type of the metric it represents. For example, "first contentful paint" is measured in milliseconds and exposed as ints, therefore its metric bins will use int32s for its start and end types. However, "cumulative layout shift" is measured in unitless decimals and is exposed as a decimal encoded as a string, therefore its metric bins will use strings for its value type.

JSON representation
{
  "start": value,
  "end": value,
  "density": number
}
Fields
start

value (Value format)

Start is the beginning of the data bin.

end

value (Value format)

End is the end of the data bin. If end is not populated, then the bin has no end and is valid from start to +inf.

density

number

The proportion of users that experienced this bin's value for the given metric.

Percentiles

Percentiles contains synthetic values of a metric at a given statistical percentile. These are used for estimating a metric's value as experienced by a percentage of users out of the total number of users.

JSON representation
{
  "p75": value
}
Fields
p75

value (Value format)

75% of users experienced the given metric at or below this value.