Timing Metrics Collected

The RUM JavaScript is the source for all RUM timing metrics. The metrics provided by the RUM JavaScript are calculated using the W3C Navigation Timing specification.

Navigation Timing is a specification from the W3C used to define a JavaScript-based performance timing interface for use with Web applications.

For a diagram showing when Navigation Timing metrics are collected, see Navigation Timing Metric Collection.

The following table describes the metrics included with RUM, as well as the collection source(s) used.

RUM Metric Data
Data Element Description
DNS lookup time The time it takes for DNS to resolve the IP address of the host.
DOM content loaded time The time it takes to load and parse a page before stylesheets, images, and other page elements are loaded.

This data element is calculated based on the difference between the DOM Content Loaded Event Start and DOM Content Loaded Event End metrics.

DOM interactive time Time until the browser finishes parsing the document, including scripts inserted in the traditional blocking way, that is, without defer or async attribute.
DOM complete time Time until the parser finishes its work on the main document. All the DOM elements on the base page have been created and rendered.
Download time The time it takes for the HTML base page to download.

This data element is calculated based on the difference between the HTTP Request Start and HTTP Response End metrics.

First byte Time until the first byte of information is received, either from the edge or from origin.
First Paint Time Time until the first pixel appears on the screen.
Page load time Time until the browser returns the onload event, indicating that any additional application logic is complete. Additional scripts can be set to run at this time, or to run continuously.
SSL start time The time it takes to negotiate SSL encryption.
TCP connection time The time it takes to establish the TCP/IP connection between the end user and the Edge.

This data element is calculated based on the difference between the TCP Connection Start and TCP Connection End metrics.