How to send large files without uploading them anywhere

Q: What is the size limit?

Up to 10 GB per transfer with [Wormhole](/directory/wormhole). Files below about 5 GB can move peer-to-peer if both tabs stay open.

Short answer

You don't need a cloud account to send a large file — and you don't need to trust anyone with its contents. Tools like Wormhole encrypt the file in your browser before anything is transmitted, and put the decryption key in the part of the link after the # symbol, which browsers never send to the server. The service therefore stores a blob it cannot open. Files up to 10 GB work, nothing is installed, and the transfer expires by itself after 24 hours.

Why the # in the link matters

Everything after the # in a URL is called the fragment. It is the one part of an address that browsers deliberately do not transmit: it stays on your machine and is used locally, for scrolling to an anchor. Encrypted transfer tools exploit that. The file is encrypted in your browser, the encrypted blob is uploaded, and the key is written into the fragment of the link you share.

The consequence is worth stating plainly: the operator of the service holds your file but cannot read it, because the key never reached them. That is not a policy they could change tomorrow — it is a property of how the link is built. It also means the link IS the key, which has its own implications, covered below.

Mentioned here: 🌀 Wormhole, 🔐 CryptPad, 🗜️ Squoosh

The practical route

Open the tool, drag the file in, wait for the browser to encrypt and upload it, copy the link, send the link. There is no account step and nothing to install. On a phone it is the same three actions.

For files up to roughly 5 GB the transfer can go peer-to-peer while both tabs are open — the file passes directly from your machine to theirs and no server holds a copy at all. Above that, or if you close the tab, the encrypted copy on the server takes over.

What to be careful about

Treat the link like the file itself. Anyone holding it can download and decrypt — so send it over a channel you would be comfortable sending the file over, and never paste it somewhere public.

The 24-hour expiry is a feature for privacy and a problem for archiving. If the recipient is on holiday, the file is gone. For anything that must stay available, this is the wrong tool.

Encryption happens on your device, so very large files are bounded by its memory. A 9 GB transfer that a laptop handles comfortably can fail on an older phone.

Frequently asked

Is it really end-to-end encrypted?

Yes, in the strict sense: the key is generated in your browser and lives in the URL fragment, which is never sent to the server. The service stores ciphertext it has no way to decrypt.

What is the size limit?

Up to 10 GB per transfer with Wormhole. Files below about 5 GB can move peer-to-peer if both tabs stay open.