Performance Metrics

Learn how to attach performance metrics to your transactions.

Sentry's SDKs support sending performance metrics data to Sentry. These are numeric values attached to transactions that are aggregated and displayed in Sentry.

The JavaScript Browser SDKs automatically collect the following performance metrics:

  • First Paint: fp
  • First Contentful Paint: fcp
  • Largest Contentful Paint: lcp
  • First Input Delay: fid
  • Cumulative Layout Shift: cls
  • Time to First Byte: ttfb
  • Time to First Byte Request Time: ttfb.requesttime

In addition to automatic performance metrics, the SDK supports setting custom performance measurements on transactions. This allows you to define measurements that are important to your application and send them to Sentry.

To set a performance measurement, you need to supply the following:

  • name (string)
  • value (any numeric type - float, integer, etc.)
  • unit (string, defaults to the string none if omitted)

Sentry supports adding arbitrary custom units, but we recommend using one of the supported units listed below.

Adding custom measurements is supported in Sentry's JavaScript SDK version 7.0.0 and above.

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// Record amount of memory used
Sentry.setMeasurement("memoryUsed", 123, "byte");

// Record time when Footer component renders on page
Sentry.setMeasurement("ui.footerComponent.render", 1.3, "second");

// Record amount of times localStorage was read
Sentry.setMeasurement("localStorageRead", 4);

Currently, unit conversion is only supported once the data has already been stored. This means that, for example, ('myMeasurement', 60, 'second') and ('myMeasurement', 3, 'minute') would not be aggregated, but rather stored as two separate measurements. To avoid this, make sure to use a consistent unit when recording a custom measurement.

Units augment measurement values by giving meaning to what otherwise might be abstract numbers. Adding units also allows Sentry to offer controls - unit conversions, filters, and so on - based on those units. For values that are unitless, you can supply an empty string or none.

  • nanosecond
  • microsecond
  • millisecond
  • second
  • minute
  • hour
  • day
  • week

  • bit
  • byte
  • kilobyte
  • kibibyte
  • megabyte
  • mebibyte
  • gigabyte
  • gibibyte
  • terabyte
  • tebibyte
  • petabyte
  • pebibyte
  • exabyte
  • exbibyte

  • ratio
  • percent

If you want to explore further, you can find details about supported units in our event ingestion documentation.

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