How it works
From your file picker to their device.
A Dropfile transfer has a short coordination stage followed by a live browser-to-browser data connection. Here is what happens at each step.
The sender chooses one file
The browser receives access only to the file the sender selects. Choosing a file does not upload it. Dropfile reads it in pieces later, when an authorized recipient starts downloading.
Dropfile creates temporary access
The sender chooses a 15-minute or one-hour availability window and either one-person or multi-download mode. A random share identifier, control token, password-derived proof, file metadata, and expiry time are registered for coordination.
The recipient proves access
The download page first checks that a person is present with Cloudflare Turnstile. The recipient then enters the password supplied by the sender. The password is processed in the recipient's browser before the server checks a derived proof.
WebRTC connects the browsers
Once access is approved, the browsers exchange connection descriptions through Dropfile's signaling service. WebRTC data channels carry file pieces directly between participating peers when the network path permits it.
The browser verifies and saves pieces
Each piece is hashed and signed by the sender. The recipient verifies it before writing the data. Desktop browsers with the File System Access API can stream to a chosen destination; other browsers may use device storage managed by the browser before saving.
Expiration stops new joins
After the selected window ends, new recipients cannot unlock the share. A transfer that already started may finish while its participating browsers remain connected. Closing the sender tab, sleeping the device, or losing connectivity can interrupt delivery.