This feature is non-standard and is not on a standards track. Do not use it on production sites facing the Web: it will not work for every user. There may also be large incompatibilities between implementations and the behavior may change in the future.

The non-standard, Firefox-specific the HTMLCanvasElement method mozGetAsFile() returns a memory-based File object representing the image contained in the canvas.


canvas.mozGetAsFile(name, type);


A DOMString indicating the file name to give the file representing the image file in memory.
type Optional
A DOMString which specifies the image file format to use when creating the new image file. The default type is image/png. For other options, see our Image file type and format guide.

Return value

A File object representing the image contained in the canvas. The file's data is entirely located in memory until such time as it is explicitly written to disk.


This example creates an image file from the <canvas> element on the page, then uses a FileReader to read the image data from the file.


<canvas id="canvas" width="100" height="100"></canvas>
<p><a href="#" id="link">Click here to try out mozGetAsFile()</a>.</p>


The following code uses mozGetAsFile() to create a File object from the canvas and appends it as an image to the page by loading it as a data URL using the readAsDataURL() method. Then a new <img> element is created using the new data URL.

function draw() {
  var canvas = document.getElementById('canvas');
  var ctx = canvas.getContext('2d');

  ctx.fillStyle = 'rgb(200, 0, 0)';
  ctx.fillRect(10, 10, 55, 50);

  ctx.fillStyle = 'rgba(0, 0, 200, 0.5)';
  ctx.fillRect(30, 30, 55, 50);

  var link = document.getElementById('link');
  link.addEventListener('click', copy);

function copy() {
  var canvas = document.getElementById('canvas');
  var f = canvas.mozGetAsFile('test.png');
  var reader = new FileReader();

  reader.onloadend = function() {
   var newImg = document.createElement('img');
   newImg.src = reader.result;

window.addEventListener('load', draw);


Not part of any specification.

Browser compatibility

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