Upload base64 image with Ajax

My client is offering the user to pick a picture, crop and resize it and then display it (in a <img> DOM element).
If the picture is fine, the user can upload it to the server so it can be saved.

I would like to do the upload thanks to an Ajax request.

I found tons of examples on the internet to upload the original image retrieved from the client PC. For instance:

$( '#my-form' )
  .submit( function( e ) {
    $.ajax( {
      url: 'http://host.com/action/',
      type: 'POST',
      data: new FormData( this ),
      processData: false,
      contentType: false
    } );
  } );

This works properly if I decide to upload the picture retrieved through the form input.

In my case I want to upload the modified picture (saved in a <img> element) instead of the original one.
This picture is stored as a base64 picture (For information: I used the croppie.js library to generate the image).

I don't know how to upload this picture with Ajax.

I tried to upload it as a regular parameter but on the server side the img is an empty string:

var url = 'http://host.com/action/';
var data = {};
data.img = $('img#generated-image').attr('src');

$.ajax({url: url, type: "POST", data: data})
    // Do something
// RESULTS in a empty data.img on the server side.

My problem being the server having an empty string when retrieving the "img" parameter. I suspect the image is maybe too big to be passed to the server or some other issues that I don't understand... .

So I'm wondering what is the proper way to send a base64 image to the server using an Ajax request WITHOUT using a form.

Thanks for your help.


Seems to be an xmlHTTP POST parameter size issue. I tried to reduce the number of characters of the string representation of the image and the server is now able to retrieve it.


post_max_size is set to 8M in the php.ini file wheras the picture size is only 24K. So the problem is not there.
I'm using PHP with the Symfony2 framework.
Maybe a limitation from Symfony2.



I finally decided to convert the base64 image to a Blob so it can be sent via an Ajax request with the formData object as follows. It saves upload bandwidth (base64 takes 33% more bits than its binary equivalent) and I couldn't find the reason for no transmission of base64 parameter (due to size limitation somewhere for sure).

The base64ToBlob function is based on this answer to another question.

function base64ToBlob(base64, mime) 
    mime = mime || '';
    var sliceSize = 1024;
    var byteChars = window.atob(base64);
    var byteArrays = [];

    for (var offset = 0, len = byteChars.length; offset < len; offset += sliceSize) {
        var slice = byteChars.slice(offset, offset + sliceSize);

        var byteNumbers = new Array(slice.length);
        for (var i = 0; i < slice.length; i++) {
            byteNumbers[i] = slice.charCodeAt(i);

        var byteArray = new Uint8Array(byteNumbers);


    return new Blob(byteArrays, {type: mime});

My JS code:

var url = "url/action";                
var image = $('#image-id').attr('src');
var base64ImageContent = image.replace(/^data:image\/(png|jpg);base64,/, "");
var blob = base64ToBlob(base64ImageContent, 'image/png');                
var formData = new FormData();
formData.append('picture', blob);

    url: url, 
    type: "POST", 
    cache: false,
    contentType: false,
    processData: false,
    data: formData})

In Symfony2 I can retrieve the image thanks to:

$picture = $request->files->get('picture');

Nitseg's answer works nicely. Also, I wanted to add the following lines if you must use auth token in your ajax call. Again, take a look at Nitseg's answer for more details first.

var formData = new FormData();
var token = "<YOUR-TOKEN-HERE>";
formData.append("uploadfile", mediaBlob);        

    url: url,
    type: "POST",
    cache: false,
    contentType: false,
    processData: false,
    data: formData,
    beforeSend: function (xhr){ 
        xhr.setRequestHeader("Authorization", "Bearer " + token); 
.done((e) => {
    // It is done.
.fail((e) => {
    // Report that there is a problem!


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