How WispFile works
WispFile sends files straight from your device to the other person’s. They are never uploaded anywhere first, so there is nothing to store, nothing to expire and no size limit.
1. You pick files and get a link
Your browser creates a random 256-bit key and puts it at the end of the link, after the #. Browsers never send that part of a link to a server, so WispFile never sees the key. It only learns the names and sizes of the files, so the receiver can see what is on offer.
2. They open the link while you are online
The two browsers find each other through WispFile’s signaling service, then connect directly with WebRTC. On most networks the files go device to device. When a strict network makes that impossible, paid plans fall back to a relay that passes the encrypted bytes along without storing them and can no more read them than anyone else. Free links are direct only.
3. Every piece is encrypted and checked
Each piece of each file is encrypted with AES-GCM using the key from the link and carries a fingerprint of its contents. The receiver checks both before writing a byte, so a damaged or altered piece is fetched again rather than saved.
4. It saves as it goes, and survives a dropped connection
On Chrome and Edge the files are written straight into the folder you choose; elsewhere they arrive as a normal download, and several files come as one zip. If the connection drops, the download waits and continues from where it stopped once both sides are back.
What to know
- Keep the page open while sending. The files come from your device, so the link works only while you are sharing.
- A password adds a second lock. With one, the link carries the key encrypted, and only someone with the password can open it. Send the password another way.
- Links can expire when you stop sharing, after one download, or after 24 hours.