PerformanceResourceTiming

The PerformanceResourceTiming interface enables retrieving and analyzing detailed network timing data regarding the loading of an application's resources. An application can use the timing metrics to determine, for example, the length of time it takes to fetch a specific resource, such as an XMLHttpRequest, <SVG>, image, or script.

The interface's properties create a resource loading timeline with high-resolution timestamps for network events such as redirect start and end times, fetch start, DNS lookup start and end times, response start and end times, etc. Additionally, the interface extends performance entries with other properties which provide data about the size of the fetched resource as well as the type of resource that initiated the fetch.

This interface extends the following PerformanceEntry properties by qualifying and constraining these properties for performance entries with an entry type of "resource":

• PerformanceEntry.entryType - Set to "resource".
• PerformanceEntry.name - Set to the resource's URL.
• PerformanceEntry.startTime - Set to the timestamp immediately before the browser to fetch the resource.
• PerformanceEntry.duration - Set to the difference between the resource's responseEnd timestamp and its startTime timestamp.

Properties

The timing properties given below are listed in the order in which they are recorded for the fetching of a single resource. An alphabetical listing is shown in the navigation, at left.

PerformanceResourceTiming.initiatorTypeRead only

A string representing the type of resource that initiated the performance entry, as specified in PerformanceResourceTiming.initiatorType.

PerformanceResourceTiming.nextHopProtocolRead only

A string representing the network protocol used to fetch the resource, as identified by the ALPN Protocol ID (RFC7301).

PerformanceResourceTiming.workerStartRead only

If the current context is a worker, returns the DOMHighResTimeStamp immediately before the worker is started that fetches the resource; otherwise zero is returned.

PerformanceResourceTiming.redirectStartRead only

A DOMHighResTimeStamp that represents the start time of the fetch which initiates the redirect.

PerformanceResourceTiming.redirectEndRead only

A DOMHighResTimeStamp immediately after receiving the last byte of the response of the last redirect.

PerformanceResourceTiming.fetchStartRead only

A DOMHighResTimeStamp immediately before the browser starts to fetch the resource.

PerformanceResourceTiming.domainLookupStartRead only

A DOMHighResTimeStamp immediately before the browser starts the domain name lookup for the resource.

PerformanceResourceTiming.domainLookupEndRead only

A DOMHighResTimeStamp representing the time immediately after the browser finishes the domain name lookup for the resource.

PerformanceResourceTiming.connectStartRead only

A DOMHighResTimeStamp immediately before the browser starts to establish the connection to the server to retrieve the resource.

PerformanceResourceTiming.connectEndRead only

A DOMHighResTimeStamp immediately after the browser finishes establishing the connection to the server to retrieve the resource.

PerformanceResourceTiming.secureConnectionStartRead only

A DOMHighResTimeStamp immediately before the browser starts the handshake process to secure the current connection.

PerformanceResourceTiming.requestStartRead only

A DOMHighResTimeStamp immediately before the browser starts requesting the resource from the server.

PerformanceResourceTiming.responseStartRead only

A DOMHighResTimeStamp immediately after the browser receives the first byte of the response from the server.

PerformanceResourceTiming.responseEndRead only

A DOMHighResTimeStamp immediately after the browser receives the last byte of the resource or immediately before the transport connection is closed, whichever comes first.

PerformanceResourceTiming.transferSizeRead only

A number representing the size (in octets) of the fetched resource. The size includes the response header fields plus the response payload body.

PerformanceResourceTiming.encodedBodySizeRead only

A number representing the size (in octets) received from the fetch (HTTP or cahce), of the payload body, before removing any applied content-codings.

PerformanceResourceTiming.decodedBodySizeRead only

A number that is the size (in octets) received from the fetch (HTTP or cache) of the message body, after removing any applied content-codings.

Methods

PerformanceResourceTiming.toJSON()

Returns a DOMString that is the JSON representation of the PerformanceResourceTiming object.

Example

See the example in Using the Resource Timing API.

Specifications

Browser compatibility

See also

• Resource Timing (Overview)
• Using the Resource Timing API