What happens when I share a file?
A classic transfer service works in two halves: you upload the whole file to a server, then the recipient downloads it from there. StrongFolder removes the server in the middle. When you pick files, your browser only reads their names and sizes and creates a session; the data stays on your disk. The link you send points to that session.
When the recipient opens the link, a small signalling service introduces the two browsers to each other. They exchange network details and open a direct WebRTC data channel — the same kind of connection browsers use for video calls. From then on the files flow from your device to theirs, piece by piece, while both tabs are open.
Why is there no upload bar?
Because nothing is uploaded. With a cloud service you first wait for 100% upload, and only then can anyone download. With StrongFolder the recipient starts receiving the first bytes as soon as the connection is up. For big files this often halves the total time: there is one transfer instead of two.
How fast is a direct transfer?
A direct transfer runs at the speed of the slower side: usually the sender's upload speed. At 50 Mbit/s upload, 10 GB takes roughly 27 minutes; at 500 Mbit/s, under 3 minutes. Both devices on the same office or home network can be much faster. A relayed connection is usually slower than a direct one.
| Your upload speed | 1 GB | 10 GB | 100 GB |
|---|---|---|---|
| 10 Mbit/s | ~13 min | ~2.2 h | ~22 h |
| 50 Mbit/s | ~3 min | ~27 min | ~4.4 h |
| 100 Mbit/s | ~1.3 min | ~13 min | ~2.2 h |
| 500 Mbit/s | ~16 s | ~3 min | ~27 min |
Theoretical times at a steady speed (1 GB = 1,000 MB); real transfers are a little slower.
How are folders sent?
When you choose a folder, StrongFolder shares the whole tree: every subfolder and file name. On the recipient's side, Chrome, Edge, Opera and other Chromium browsers on a computer can write the same tree straight to disk, file by file, without zipping. Other browsers download the files one by one or as a ZIP. See How to send a folder without zipping.
What do I need?
- Sender: A modern browser with WebRTC; Google Chrome or another Chromium browser on a computer works best. The Chrome extension adds a one-click button to Chrome.
- Recipient: any modern browser; Chrome, Edge or Opera on a computer to save whole folders.
- Both: an internet connection at the same time. The sender's tab stays open until the end.
Full list: Limits & requirements.
Free · in your browser · no sign-up
Web app or Chrome extension?
Both do the same transfer. The web app works in any browser, on any computer. The Chrome extension puts StrongFolder next to the address bar, so you can share a file or folder from any page in one click.