The decodedBodySize read-only property returns the size (in octets) received from the fetch (HTTP or cache) of the message body, after removing any applied content-codings. If the resource is retrieved from an application cache or local resources, it returns the size of the payload after removing any applied content-codings.

Note: This feature is available in Web Workers.



Return value

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


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

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

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

  if ("transferSize" in perfEntry)
    console.log("transferSize = " + perfEntry.transferSize);
    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++) {


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

Browser compatibility

Update compatibility data on GitHub
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidEdge MobileFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
Basic supportChrome Full support 54Edge Full support 17Firefox No support NoIE No support NoOpera Full support 41Safari No support NoWebView Android Full support 54Chrome Android Full support 54Edge Mobile No support NoFirefox Android No support NoOpera Android Full support 41Safari iOS No support NoSamsung Internet Android Full support 6.0


Full support  
Full support
No support  
No support

Document Tags and Contributors

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