blueimp/jquery-file-upload

jQuery File Upload is a plug-in for the jQuery JavaScript library that adds a polished file-upload experience to any web page. Instead of a plain file input that sends one file at a time and shows no feedback, this widget lets visitors select multiple files at once, drag and drop them from their desktop directly onto the browser window, watch individual progress bars as each file transfers, cancel an upload mid-way, and resume it later if the connection drops. It handles large files by splitting them into smaller chunks and sending those pieces one by one, useful when uploading videos or archives over a slow connection. Before a file even leaves the browser, images can be resized on the client side, and the user can see a preview of images, audio clips, or video files they have selected. No browser plug-ins such as Flash are needed because everything is built on standard HTML and JavaScript. The server side is deliberately not tied to any particular language or framework. Because it relies on standard HTML form file uploads under the hood, any backend, PHP, Python, Ruby on Rails, Java, Node.js, Go, or others, can receive the uploaded data without special configuration. A developer would add this to a project whenever they need a richer upload interface than the browser's default file picker: a photo gallery that lets users drag in batches of images, an admin panel that accepts large CSV exports, or any form that benefits from real-time upload progress feedback. It is written in PHP for the demo server component but is primarily a JavaScript client-side library.