When you upload an image to Summernote editor, it will convert the image to base64 data. And base64 is larger than the original data size. So in this post, I will explain how to upload the picture to Azure Storage instead of converting to base64.

Very roughly, the final size of Base64-encoded binary data is equal to 1.37 times the original data size + 814 bytes (for headers). Wikipedia


Install and setup the Azure Storage.


Create a controller to upload the picture to Azure Storage. It's simply get the request file, upload, that's it.

public class SummernoteController : Controller
    private readonly IAzureFileUploaderService _azureFileUploaderService;

    public SummernoteController(IAzureFileUploaderService azureFileUploaderService)
        _azureFileUploaderService = azureFileUploaderService;

    public async Task<ActionResult> ImageUpload()
        var files = Request.Files;
        var url = string.Empty;
        if (files.Count > 0)
            url = await _azureFileUploaderService.UploadPhotoAsync(files[0], Global.Full, "summernote");
        return Json(url);


We'll be using onImageUpload from summernote. Documentation

    height: 200,
    onImageUpload: function (files) {
        sendFile(files[0], this);

The el parameter is basically the summernote DOM element. We need this to update the insert the uploaded picture from Azure Storage.

function sendFile(file, el) {
    var formdata = new FormData();
    formdata.append(file.name, file);
    var xhr = new XMLHttpRequest();
    xhr.open('POST', '/summernote/ImageUpload/');
    xhr.onreadystatechange = function () {
        if (xhr.readyState == 4 && xhr.status == 200) {
            var response = xhr.response.replace(new RegExp('"', 'g'), '');
            $(el).summernote('insertImage', response, file.name);
    return false;

First, we create a FormData object, append the file, post an http post request to the controller we created above. When it's done, call insertImage. Documentation

Done! :)