PerformanceResourceTiming
The PerformanceResourceTiming
interface enables retrieval and analysis of 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 PerformanceEntry
with other properties which provide data about the size of the fetched resource as well as the type of resource that initiated the fetch.
Note: This feature is available in Web Workers
Properties
This interface extends the following PerformanceEntry
properties for resource performance entry types by qualifying and constraining them as follows:
PerformanceEntry.entryType
Read only-
Returns
"resource"
. PerformanceEntry.name
Read only-
Returns the resources URL.
PerformanceEntry.startTime
Read only-
Returns the
timestamp
for the time a resource fetch started. This value is equivalent toPerformanceResourceTiming.fetchStart
. PerformanceEntry.duration
Read only-
Returns a
timestamp
that is the difference between theresponseEnd
and thestartTime
properties.
The interface also supports the following properties which 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.initiatorType
Read only-
A
string
representing the type of resource that initiated the performance entry, as specified inPerformanceResourceTiming.initiatorType
. PerformanceResourceTiming.nextHopProtocol
Read only-
A
string
representing the network protocol used to fetch the resource, as identified by the ALPN Protocol ID (RFC7301). PerformanceResourceTiming.workerStart
Read only-
Returns a
DOMHighResTimeStamp
immediately before dispatching theFetchEvent
if a Service Worker thread is already running, or immediately before starting the Service Worker thread if it is not already running. If the resource is not intercepted by a Service Worker the property will always return 0. PerformanceResourceTiming.redirectStart
Read only-
A
DOMHighResTimeStamp
that represents the start time of the fetch which initiates the redirect. PerformanceResourceTiming.redirectEnd
Read only-
A
DOMHighResTimeStamp
immediately after receiving the last byte of the response of the last redirect. PerformanceResourceTiming.fetchStart
Read only-
A
DOMHighResTimeStamp
immediately before the browser starts to fetch the resource. PerformanceResourceTiming.domainLookupStart
Read only-
A
DOMHighResTimeStamp
immediately before the browser starts the domain name lookup for the resource. PerformanceResourceTiming.domainLookupEnd
Read only-
A
DOMHighResTimeStamp
representing the time immediately after the browser finishes the domain name lookup for the resource. PerformanceResourceTiming.connectStart
Read only-
A
DOMHighResTimeStamp
immediately before the browser starts to establish the connection to the server to retrieve the resource. PerformanceResourceTiming.connectEnd
Read only-
A
DOMHighResTimeStamp
immediately after the browser finishes establishing the connection to the server to retrieve the resource. PerformanceResourceTiming.secureConnectionStart
Read only-
A
DOMHighResTimeStamp
immediately before the browser starts the handshake process to secure the current connection. PerformanceResourceTiming.requestStart
Read only-
A
DOMHighResTimeStamp
immediately before the browser starts requesting the resource from the server. PerformanceResourceTiming.responseStart
Read only-
A
DOMHighResTimeStamp
immediately after the browser receives the first byte of the response from the server. PerformanceResourceTiming.responseEnd
Read 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.transferSize
Read 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.encodedBodySize
Read only-
A
number
representing the size (in octets) received from the fetch (HTTP or cache), of the payload body, before removing any applied content-codings. PerformanceResourceTiming.decodedBodySize
Read 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. PerformanceResourceTiming.serverTiming
Read only-
An array of
PerformanceServerTiming
entries containing server timing metrics.
Methods
PerformanceResourceTiming.toJSON()
-
Returns a
DOMString
that is the JSON representation of thePerformanceResourceTiming
object.
Example
See the example in Using the Resource Timing API.
Specifications
Specification |
---|
Resource Timing Level 2 # resources-included-in-the-performanceresourcetiming-interface |
Browser compatibility
BCD tables only load in the browser