hi,
1.Sorry, we can't load the ImageTarget by url, but video is ok.
2.You can view this document and it will help you learn more, https://www.easyar.com/doc/EasyAR%20SDK/Unity%20Plugin%20Reference/1.0/ImageTarget.html?highlight=json.
3.If you want to use the url path, you can use EasyAR CRS( Cloud Recognition Service ). EasyAR CRS provides both image retrieval and target management as web services and supports 100k target images.You can visit this document, https://www.easyar.com/doc/EasyAR%20CRS/EasyAR%20CRS.html .