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PerformanceResourceTiming.transferSize

The transferSize read-only property represents the size (in octets) of the fetched resource. The size includes the response header fields plus the response payload body (as defined by RFC7230.

Note: This feature is available in Web Workers.

If the resource is fetched from a local cache, or if it is a cross-origin resource, this property returns zero.

Syntax

resource.transferSize;

Return value

A number representing the size (in octets) of the fetched resource. The size includes the response header fields plus the response payload body (RFC7230).

Example

The following example, the value of size properties of all "resource" type events are logged.

function log_sizes(perfEntry){
  // Check for support of the PerformanceEntry.*size properties and print their values
  // if supported.
  if ("decodedBodySize" in perfEntry)
    console.log("decodedBodySize = " + perfEntry.decodedBodySize);
  else
    console.log("decodedBodySize = NOT supported");

  if ("encodedBodySize" in perfEntry)
    console.log("encodedBodySize = " + perfEntry.encodedBodySize);
  else
    console.log("encodedBodySize = NOT supported");

  if ("transferSize" in perfEntry)
    console.log("transferSize = " + perfEntry.transferSize);
  else
    console.log("transferSize = NOT supported");
}
function check_PerformanceEntries() {
  // Use getEntriesByType() to just get the "resource" events
  var p = performance.getEntriesByType("resource");
  for (var i=0; i < p.length; i++) {
    log_sizes(p[i]);
  }
}

Specifications

Specification Status Comment
Resource Timing Level 1
The definition of 'transferSize' in that specification.
Candidate Recommendation Initial definition.

Browser compatibility

FeatureChromeEdgeFirefoxInternet ExplorerOperaSafari
Basic support54 No No No41 No
FeatureAndroid webviewChrome for AndroidEdge mobileFirefox for AndroidOpera AndroidiOS SafariSamsung Internet
Basic support5454 No No41 No6.0

Document Tags and Contributors

Contributors to this page: fscholz, chrisdavidmills, OliverJAsh2, jpmedley, rolfedh, AFBarstow
Last updated by: fscholz,