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Uploading

Drag files onto the file list, or use the upload button. Uploads happen in your browser and you can watch each one progress.
Do not close the tab mid-upload. Encryption happens in the page, so closing it stops the upload. An interrupted upload leaves nothing usable behind, and the partial data is cleaned up rather than charged to your quota.

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Limits

Files are encrypted and uploaded in 4 MiB chunks, so a large file does not have to be held in memory all at once.

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What gets encrypted

Everything that describes your file, not just its bytes: The server never learns any of them.
Because names are encrypted, the server cannot sort or search by them. Cloud fetches your list and sorts and searches it in your browser after decrypting. This is why a very large folder takes a moment to settle.
The size of each file is visible to the server — encrypted data is roughly the same length as the original, and quota has to be counted somehow. See what the server can see.

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Thumbnails

For images, Cloud generates a small preview in your browser, encrypts it, and stores it alongside the file. Grid view decrypts thumbnails as you scroll. Thumbnails are generated locally, so the server never receives an unencrypted version of any image — including the small one.

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Quota

Your usage counts the encrypted bytes, which is what is actually stored. Authentication data adds about 0.0004% over the original size, which is close enough that the interface shows one number. If an upload would exceed your allowance it is refused before anything is transferred, rather than part-way through. Two uploads running at once cannot both slip past the limit. Version history counts against your quota as well, and the storage panel breaks out how much of your usage is history — see Version history.

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Duplicate names

Two files cannot have the same name in the same folder, and Cloud enforces that without ever learning either name: your browser computes an opaque value from the name and the folder’s key, and the server only ever compares those values for equality. Because the value is keyed on the parent folder, the same filename in two different folders produces two unrelated values — nothing leaks across folders either.

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Downloading

Select a file and download it. Chunks are fetched, verified and decrypted in your browser, then assembled into the file you get. Each chunk is bound to its position in the file, so a truncated, reordered, or substituted download fails cleanly rather than producing a corrupted file that looks fine.

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Previewing without downloading

Files above 150 MB are not previewed inline regardless of type.
PDFs are deliberately not previewed. Rendering one would mean handing a decrypted document to a viewer running on the page that is holding your keys. Until that can be isolated properly, Cloud offers a download instead.

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Uploading from Compose or Snap

Not yet. Automatic syncing from the desktop apps is designed but not built, so uploading a .course file or a capture is something you do yourself through the browser today.