Security

Built so there is nothing on our servers to lose

Last updated August 20, 2026

The short version

FileTransferX moves files directly between two browsers instead of uploading them to us. Our server's only job is to help two devices find each other — it never receives, stores, or reads your files. Connections are encrypted end-to-end, pairing codes are short-lived and single-use, and closing the tab ends the session immediately. This page explains exactly what that means, piece by piece.

Files are transferred browser-to-browser

When a transfer runs, file data moves directly between the sending and receiving browser over a connection each browser negotiates and encrypts end-to-end on its own — the file data inside it isn't something a server in the middle can read, whether or not one happens to be forwarding traffic. FileTransferX's own infrastructure is only involved in helping the two browsers agree on how to connect; it is not a party the file data is addressed to.

FileTransferX does not store uploaded files

There is no upload step. Files are read and sent in small chunks straight from the sender's device toward the receiver's, and FileTransferX never writes those chunks to a database or a file store on our end — including during a relayed transfer, where the relay only forwards encrypted bytes it cannot decrypt. Once a chunk is delivered, there is nothing left behind to retain, back up, or accidentally leak later, because it was never saved anywhere but the two devices involved.

What our server can and cannot see

Our server's job is narrow: introduce two browsers to each other so they can open a direct connection. That limited role defines a hard boundary on what it is ever exposed to.

Can see

  • That a pairing session exists, identified only by a short-lived transfer code.
  • The connection setup messages two browsers exchange to link up, and the network address information needed to find a path between them.
  • Timing — when a session was created, when two devices connected, and when it ended.

Cannot see

  • File names, file types, thumbnails, or any file contents — files never pass through our server in a readable form.
  • The contents of your transfer even when a relay forwards it — that path carries encrypted data it cannot decrypt.
  • Who you are — there are no accounts, logins, or personal details tied to a session.
  • Any history after a session ends — nothing about a completed or abandoned transfer is kept.

What information is temporarily exchanged

Pairing two devices requires a small amount of setup data to flow through our server. None of it is file data, and none of it outlives the session it belongs to.

When a session expires

A transfer code is tied to a single pairing attempt. It stops working as soon as a receiving device successfully pairs with it, if it goes unused for a short window, or once the transfer it was created for finishes, is cancelled, or disconnects. There's no long-lived session store behind it — an expired or completed session simply leaves nothing behind to expire "from" later. If you need to send again, starting a new session generates a fresh code.

Why closing the browser ends the transfer

The connection between the two devices and any in-progress file data exist only inside the sending and receiving tabs' own memory — there is no background job on a server carrying the transfer forward. Closing, refreshing, or navigating away from the tab ends that connection immediately, which stops the transfer on the spot. This isn't a limitation so much as a direct consequence of not storing files: with nothing persisted server-side, there is nothing to resume a transfer from once the browser that was moving the data is gone.

Direct vs. relayed transfer

FileTransferX always attempts a direct connection first. Some networks — strict corporate firewalls, certain mobile carriers — block that path outright, so a fallback exists to keep transfers working everywhere.

Device A
Direct connection
Device B

If a direct connection can't be established

Device A
Secure relay
Device B
Direct connection

Data flows on a straight line between the two browsers. No third party sits on the data path at all, so there's nothing between the devices that could see, log, or intercept the transfer even in principle.

Secure relay

Used only when a direct path can't be established. A relay forwards the same encrypted data between the two devices without decrypting it — it moves encrypted bytes, not readable files.

Found a security issue?

If you believe you've found a vulnerability in FileTransferX, please report it to us directly rather than disclosing it publicly, and we'll follow up as soon as we can.

Email us