Cryptomator
FreeEncrypt files before they hit the cloud — the key stays with you
Open Source No Ads No Tracking No Sign-up Cross-platform
Client-side encryption for your cloud files, protecting both contents and filenames with AES-256. Create an encrypted vault before syncing to Dropbox, Google Drive, OneDrive and more — the provider never sees plaintext. The desktop apps are fully free; the iOS and Android apps are read-only for free, with write access unlocked by a one-time in-app purchase.