Uppy - The next open source file uploader for web browsers
CloudExplorer - Cloud Explorer is a open-source Amazon S3 client.
Uploadcare - File uploading, media processing & content delivery for modern web apps
StackPath - Secure Content Delivery Network, DDoS, WAF Service
Filestack - Simple file uploader and robust APIs for uploading, transforming, and delivering any file into your app. Filestack is a collection of tools and powerful APIs that make it simple to upload, transform, and deliver content.
AssetPicker - A free, easy to use, cross plattform ready asset or file picker.