User action metrics

For web applications, Dynatrace calculates the following user action metrics.

Milestone metrics

Milestone metrics represent events that occur at a specific point in time during a user action. However, they are measured in (m)sec, because they are calculated relative to the user action start time. In other words, user action start time serves as a reference point from which the time for the milestone metrics is measured. A value for example of 47msec for Navigation start indicates that this event occurred 47msec after the action start time.

Metric Description Applicable to
Navigation start The moment right after the prompt for unload terminates on the previous document in the same browsing context (if there is no previous document, this value is the same as PerformanceTiming.fetchStart)). Load actions
Request start The moment the user agent sends the request to obtain the actual document, from the server, relevant application caches or from local resources (if the transport layer fails after the start of the request and the connection is reopened, this property will be set to the time corresponding to the new request). Load actions
Time to first byte The moment the first byte of a response is received from the server, relevant application caches, or a local resource. Load actions
HTML downloaded The moment the last byte of the current page is received, or before the transport connection is closed (whichever occurs first). Load actions
DOM interactive The moment the parser completes its work on the main document, before a page’s readiness status is set to "interactive" (i.e., before a page is ready to receive further user input). Load actions
Speed index A score indicating how quickly the page contents are visually populated. A low Speed index means that most parts of a page are rendering quickly. Load actions
Visually complete The moment all content in the browser’s visible area is fully rendered. Load actions XHR actions
DOM content loaded The moment the user agent fires the DOMContentLoaded event at the document. Load actions
DOM complete The moment the user agent sets the current document readiness to "complete". Load actions
Load event start The moment the load event is sent for the current document. If this event has not yet been sent, it returns 0. Load actions
Load event end The moment the load event for the current page is completed. If this event has not yet been sent, or is not yet completed, it returns 0. Load actions
User action duration The moment the page load is completed. Load actions

Note:
Speed Index and Visually Complete are only available on browsers that support mutationobservers. This includes the following browsers:

  • Microsoft Internet Explorer 11
  • Microsoft Edge 15 or later
  • Firefox 57 or later
  • Google Chrome 61 or later

Phase metrics

As opposed to milestone metrics, phase metrics imply a duration.

Metric Description Applicable to
Blocking The time between the moment the browser realizes it needs to download a resource and the time that it actually starts downloading the resource. This includes the time spent on waiting for a free TCP socket, the time required for generating disk cache entries and the time spent in proxy negotiation. Load actions
Application cache The time spent checking any relevant application caches. It includes the time before the connection to the server is established. Load actions
DNS lookup The time spent on the domain name lookup for the current document. Load actions
TCP connect The time spent on establishing the connection to the server including SSL. Load actions
Secure connect The time spent on making the established connection to the server secure. This includes the SSL handshake and SOCKS. Load actions
Request The time spent on requesting the current document from the server until the first byte is received. Load actions
Response The time spent on receiving the response. Load actions
Processing The time between DOM loading and Load event start. Load actions
OnLoad The time spent on processing the load event. Load actions
OnDOMContentLoaded The time spent on executing onDomContentLoaded handlers. Load actions
Response end The elapsed time from when the first byte of the server response is received until either when the last byte of the current document of the response is received or when the response completes, whichever happens first. XHR actions
Redirect time The time spent on subsequent HTTP requests. Load actions XHR actions

Key performance metrics

From the metrics listed above, Dynatrace has specified some as key. Key performance metrics enable you to select the ideal user experience metric for each of your applications. These key metrics provide you with valuable performance insights that promote success in your digital business. The key performance metrics include:

  • User action duration
  • Visually complete
  • Speed index
  • DOM interactive
  • Load event end
  • Load event start
  • HTML downloaded
  • Time to first byte

Dynatrace allows you to choose the right performance metric for each application condition.