How to send large files without uploading them

Every mainstream way to send a large file does the same thing under the hood: it copies your file onto a company's server, then hands the other person a URL to fetch it from. WeTransfer, Dropbox, Drive, SharePoint — different interfaces, identical mechanic. The file exists twice, and the second copy is not on your machine.

There is another way to do it, and it has been built into browsers for a decade.

The short answer

A peer-to-peer transfer opens a direct connection between your browser and the recipient's, then streams the file across it. Nothing is uploaded, because there is nowhere to upload to. Combined with end-to-end encryption, it means no server ever holds a readable copy of what you sent — not for thirty days, not for thirty seconds.

What actually happens instead of an upload

The technology is WebRTC, the same stack that carries browser video calls. The sequence is short:

1. Your browser generates a key and derives it from a random secret plus a PIN. The secret lives in the link's URL fragment, after the # — a part of the URL browsers never transmit to a server.
2. A signalling server introduces the two browsers. It passes connection candidates back and forth so the two sides can find a route to each other. This is the only server involved, and it never sees file data or the key.
3. A direct channel opens between the two devices.
4. The file streams across in encrypted chunks, each one sealed with AES-256-GCM in your browser before it leaves. The recipient's browser decrypts them as they arrive and writes to disk.

At no point is there a complete copy of your file anywhere except your device and, at the end, theirs.

What you gain

The speed difference is the part people notice first. On a home connection, upload is usually far slower than download, so “upload then download” spends most of its time on your slowest link — twice over.

What you give up

This is not free of trade-offs, and a guide that pretended otherwise would be selling you something.

• Both sides have to be present. With no stored copy, there is nothing to collect later. Your tab stays open while the file streams. For a transfer you want the other person to pick up next week, a stored-copy service genuinely fits better.
• The connection has to be established. Most networks allow a direct path. Strict corporate firewalls and some mobile carriers do not, in which case the encrypted stream is relayed through a TURN server. Privacy is unaffected — the relay only ever handles ciphertext — but throughput depends on that relay.
• An interrupted transfer restarts. There is no half-uploaded file sitting on a server to resume from.

When it is clearly the right choice

• The file is sensitive and you do not want a copy outliving the handover.
• You are both available now — a call, a meeting, a live handover to a client.
• You want the recipient to need nothing: no account, no install, no app.
• Your organisation's policy is uncomfortable with third-party storage. See how to send confidential documents.

How to do it

Open SaferDrop, add the file, and share the link and PIN on separate channels. Free transfers go up to 100 MB; Pro raises that to 2 GB and adds folders and multi-file transfers. The recipient opens the link in any modern browser — nothing to install.

For the full method on big files, see how to send large files securely. For the guarantee underneath all of this, read what zero-knowledge means.

Frequently asked questions