The readAsBinaryString method is used to start reading the contents of the specified Blob or File. When the read operation is finished, the readyState becomes DONE, and the loadend is triggered. At that time, the result attribute contains the raw binary data from the file.

Note that this method was once removed from the File API specification, but re-introduced for backward compatibility.
Using FileReader.readAsArrayBuffer() is recommended.

Syntax

instanceOfFileReader.readAsBinaryString(blob);

Parameters

blob
The Blob or File from which to read.

Example

var canvas = document.createElement('canvas');
var height = 200;
var width  = 200;

canvas.width  = width;
canvas.height = height;

var ctx = canvas.getContext('2d');

ctx.strokeStyle = '#090';
ctx.beginPath();
ctx.arc(width/2, height/2, width/2 - width/10, 0, Math.PI*2);
ctx.stroke();

canvas.toBlob(function (blob) {
  var reader = new FileReader();

  reader.onloadend = function () {
    console.log(reader.result);
  }

  reader.readAsBinaryString(blob);
});

Specifications

Specification Status Comment
File API
The definition of 'readAsBinaryString' in that specification.
Working Draft  

Browser compatibility

FeatureChromeEdgeFirefoxInternet ExplorerOperaSafari
Basic support7 Yes3.610116
FeatureAndroid webviewChrome for AndroidEdge mobileFirefox for AndroidOpera AndroidiOS SafariSamsung Internet
Basic support ? Yes Yes32116.1 ?

See also

Document Tags and Contributors

Last updated by: fscholz,