Currently, many companies provide cloud storage services, but each has its own proprietary client and their functionality, as a rule, leaves much to be desired.
The existing alternatives did not suit me for many reasons, so I decided to make my own universal client - shadowcloud

Something like this:

What can

• Direct download (without using a local disk) to Google Drive, Yandex Disk (WebDAV), Cloud Mail.Ru, Dropbox
• Full default encryption, a large selection of algorithms and settings
• Password protected database
• Checksums and Deduplication
• Removes file size limit
• Replication or splitting files across different repositories
• Unlimited streaming media
• Creates previews and extracts metadata and text of documents.
• Versioning files and the entire directory structure
• Markdown notes, code highlighting
• Quick save web pages with embedded resources
• Caching files in memory
• Use as a local disk using FUSE (winfsp required)
• Open source, almost every aspect is configured via shadowcloud.conf

How to use

Actually, the repository

To use it is necessary:

• Generate an encryption key (later you need to import it on other devices)
• Configure Cloud Storage
• Create a data region and connect a storage to it (the region ID must match on all devices)

After that, you can go to the file panel, select a region and upload documents.

Little about implementation

The program is written in Scala and almost entirely built on the Akka framework (actors, streams, http, persistence), the frontend is written entirely in Scala.js.

Bouncy Castle is used for encryption and optional libsodium (default algorithms: Blake2b / ChaCha20 / ECIES / ECDSA).

Apache Tika and JavaCV are excluded from the light version because of their large size, they are used to extract metadata from documents and create previews for video recordings.