Send a big file to another device without the cloud

Two devices in the same room. One has a file the other needs. The normal answer is to upload it to a server in another country so it can be downloaded straight back to a machine three feet away.

You pay for that twice: once in the upload, which on most home connections is far slower than the download, and once in whatever the file picks up on the way through — an account, a link that works for anyone who finds it, a retention policy you didn't read.

There is a whole class of tool for this and most people never meet it.

One-off transfers: LocalSend

LocalSend is the closest thing to AirDrop that does not care what you own. Install it on both devices, open it on both, and each appears in the other's list. Pick the file, accept on the far end, done. No account, no link, no size ceiling, and the bytes never leave the network.

This is the answer to the oldest annoyance in a mixed household: getting video off an iPhone and onto a Windows laptop without iCloud in the middle.

The catch is the network. Both devices must be on the same one, and plenty of Wi-Fi has client isolation switched on — guest networks, hotels, offices, most public Wi-Fi — which stops devices seeing each other at all. If discovery silently finds nothing, that is usually why, and it is not something the app can fix. A phone hotspot with both devices joined to it is the reliable workaround.

The same two folders, forever: Syncthing

If this is not a one-off — a folder that should simply be identical on the desktop and the laptop — you want continuous sync instead of repeated sending.

Syncthing does that with no server in the middle. You introduce two machines once, tell them which folders to share, and it keeps them matched from then on. There is no storage tier to outgrow because there is no storage: it is your disks, talking.

It earns its place by being boring. Set up correctly, it runs for years without attention.

Two honest catches. The first setup is genuinely fiddly — device IDs, folder IDs, deciding which side is authoritative — and budget an evening rather than ten minutes. The second: there is no first-party iOS app, so if the phone in this story is an iPhone, this is not your tool.

Also, and this matters: sync is not backup. Delete a file on one machine and Syncthing faithfully deletes it everywhere. Versioning is a setting, and it is worth turning on.

Not on the same network: Tailscale

The local tools stop working the moment the devices are genuinely apart — laptop at a café, desktop at home.

Tailscale closes that gap by putting your own machines on a private network as though they were in one room, wherever they physically are. No port forwarding, no router configuration, no VPN config written by hand. Once it is running, the home machine has a stable address the laptop can reach from mobile data, and every tool above starts working again over that link.

The catch: the convenience depends on trusting Tailscale's coordination service to broker those connections, and the mental model — nodes, tailnet, exit nodes, access rules — takes an afternoon before it clicks. Worth it if you have more than two machines. Overkill for one transfer.

Choosing, quickly

• Once, devices side by side → LocalSend.
• The same folder on two machines, indefinitely → Syncthing, with versioning on.
• The devices are in different places → Tailscale, then either of the above across it.
• Sending to someone else, who will not install anything → this is the one case where a normal upload link is the right tool. Use one with an expiry.