Keep the cloud you already pay for, just make it unreadable
In development. Encrypts files and filenames before they sync.
Not for sale yet. In development. This page exists so you know what is coming, and so you can tell me if it is the one you want first.
When Boxcryptor shut down, a lot of people were left holding encrypted folders and no maintained tool. The alternatives are either free and rough, or they want you to move to their own cloud, which is a migration nobody asked for.
This encrypts your files on your device before they sync to Dropbox, Drive, OneDrive or iCloud. Filenames too, which matters more than people expect: a folder called Divorce with a file called settlement-final.pdf leaks the whole story without anybody opening anything.
Zero-knowledge here means the literal thing. The key is yours, I cannot read your files, and I could not hand them over if I were asked. That is a different claim from encrypted in transit while the provider keeps a copy of the key, and the difference only shows up when it matters.
What encryption does not protect you from
Worth being straight about the limits. It does not protect you from someone who has your unlocked laptop, because at that point the files are decrypted for you. It does not protect you from losing the key, and there is no recovery path, that is what zero-knowledge means in practice.
And it does not hide the fact that you have files, or how many, or when you changed them. Metadata is harder to hide than content and anyone claiming otherwise is overselling.
FAQ
What happens if I lose my key?
Your files are gone. There is no reset link, because a reset link would mean I could get in, which would mean this is not zero-knowledge. That is the real cost of the guarantee and you should decide it is worth paying before you rely on it.
Will it slow down my sync?
Encryption happens before the file leaves, so there is some local work per file. On modern hardware that is small compared with the upload itself. Very large files will feel it more.
Can I still use my cloud provider's web interface?
You can log in and you will see encrypted blobs with encrypted names, which is the point. Reading the files needs the app and your key. That includes their mobile apps, which is a real inconvenience worth knowing about up front.