The Blob interface's size property returns the size of the Blob or File in bytes.


var sizeInBytes = blob.size


The number of bytes of data contained within the Blob (or Blob-based object, such as a File).


This example uses an <input> element of type file to ask the user for a group of files, then iterates over those files outputting their names and lengths in bytes.

// fileInput is a HTMLInputElement: <input type="file" multiple id="myfileinput">
var fileInput = document.getElementById("myfileinput");

// files is a FileList object (simliar to NodeList)
var files = fileInput.files;

for (var i = 0; i < files.length; i++) {
  console.log(files[i].name + " has a size of " + files[i].size + " Bytes");


Specification Status Comment
File API
The definition of 'Blob.size' in that specification.
Working Draft Initial definition.

Browser compatibility

ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
sizeChrome Full support 5Edge Full support 12Firefox Full support 4IE Full support 10Opera Full support 11Safari Full support 5.1WebView Android No support NoChrome Android Full support 18Firefox Android No support NoOpera Android No support NoSafari iOS No support NoSamsung Internet Android Full support 1.0


Full support
Full support
No support
No support

See also