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
Resource Timing Level 2 (Resource Timing 2)
# dom-performanceresourcetiming-transfersize

Browser compatibility

Desktop Mobile
Chrome Edge Firefox Internet Explorer Opera Safari WebView Android Chrome Android Firefox for Android Opera Android Safari on IOS Samsung Internet
transferSize
54
17
45
No
41
No
54
54
45
41
No
6.0

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https://developer.mozilla.org/en-US/docs/Web/API/PerformanceResourceTiming/transferSize