Web/API/FileReader/readAsBinaryString

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

  reader.readAsBinaryString(blob);
});

Specifications

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

Browser compatibility

Update compatibility data on GitHub

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet
`readAsBinaryString`	Chrome Full support 7	Edge Full support 12	Firefox Full support 3.6	IE No support No	Opera Full support 11	Safari Full support 6	WebView Android Full support ≤37	Chrome Android Full support 18	Firefox Android Full support 32	Opera Android Full support 11	Safari iOS Full support 6.1	Samsung Internet Android Full support 1.0

Legend

Full support: Full support
No support: No support