MultCloud - Multiple Cloud Storage Manager: Migrate, move, sync, copy, backup and transfer cloud files with MultCloud, which supports Dropbox, Box, Google Drive, Mega, OneDrive and FTP, etc.

Parse - Build applications faster with object and file storage, user authentication, push notifications, dashboard and more out of the box.

Koofr - Koofr offers safe EU based cloud storage with free storage space for life and options to connect multiple cloud accounts (Dropbox, Google Drive, OneDrive) and your personal storages.

AWS Amplify - JavaScript library for app development using cloud services

odrive - odrive aggregates all cloud storage. Access, sync, share, and encrypt everything in one place. Integrations to 20+ storage services, desktop sync, Linux support, placeholder files, zero-knowledge-encryption, web client, advanced sharing, and more!

AWS Mobile Services - Storage, Analytics, Push Notif. & SMS Delivery SDKs