# Why the sender has to stay online (and how to plan for it)

Source: https://help.strongfolder.com/en/guides/why-sender-stays-online/
Updated: 2026-11-05

> In P2P file transfer the sender must stay online because the files come from the sender's device, not from a server copy. If the tab closes or the computer sleeps, the transfer stops. Plan the time from your upload speed, keep the device awake and plugged in, and use a cloud link when you can't stay connected.

Every peer-to-peer file transfer has one rule that cloud services don't: **the sender must
stay online until the recipient finishes**. It's the honest trade-off of sending files
directly. This guide explains why the rule exists, how long you actually need to stay
connected, how to keep Windows, macOS and your browser awake, and what to use instead when
you can't.

**Key facts**

- **Why:** The sender's browser tab must stay open and online until the recipient finishes downloading — files come from the sender's device, not from a server.
- **What stops a transfer:** closing the tab, clicking Stop Sharing, sleep or hibernation, lid closed on battery, losing the network.
- **How long:** about **size in GB × 8,000 ÷ upload Mbit/s** seconds — 50 GB at 50 Mbit/s ≈ 2.2 hours.
- **Plan:** plug in, disable sleep for the session, keep the tab open, avoid other big uploads.
- **Can't stay online?** Use a cloud drive or transfer service that stores a copy.

## Why does the sender have to stay online?

Because in [P2P file transfer](https://help.strongfolder.com/en/guides/p2p-file-transfer/) there is no copy anywhere else.
With a cloud service, you upload the whole file first; the provider stores it, and the
recipient downloads from the provider's servers whenever they like. With StrongFolder,
nothing is uploaded in advance. When the recipient opens the link, their browser asks yours
for the files, and your browser reads them from your disk and streams them over an
encrypted WebRTC connection.

That design is what gives P2P its advantages:

- **No upload wait** — the recipient starts immediately.
- **No stored copy** — Files are never uploaded to or stored on a StrongFolder server.
- **No size cap from the service** — there is no storage to pay for.

The same design is the reason for the rule. If your tab closes, the source disappears.
The link works while the sender keeps sharing. When the sender clicks Stop Sharing or closes the tab, the files are no longer available.

## What stops a P2P transfer?

| Event | Transfer continues? | What to do |
|---|---|---|
| You switch to another tab or app (computer) | Normally yes | Keep the StrongFolder tab open |
| You close the StrongFolder tab or the browser | **No** | Wait until the recipient finishes |
| You click **Stop Sharing** | **No** | Only when everyone has the files |
| Computer goes to sleep or hibernates | **No** | Turn off sleep for the session |
| Laptop lid closed on battery | **No** (it sleeps) | Plug in; change lid action or keep it open |
| Wi-Fi drops or you change networks | **No** | Use a stable connection; cable if possible |
| Browser discards the tab to save memory | **No** | Add the site to the "always active" list |
| Phone screen locks or browser goes to background | Often paused | Keep the page on screen while sending |

The same applies on the recipient's side: if their computer sleeps, they stop receiving.
Tell them to stay online too.

## How long do I need to stay online?

The transfer can't be faster than your **upload** speed (or the recipient's download,
whichever is slower). Best-case times for one recipient:

| Size | 20 Mbit/s upload | 50 Mbit/s upload | 100 Mbit/s upload | 500 Mbit/s upload |
|---|---|---|---|---|
| 5 GB | ~33 min | ~13 min | ~7 min | ~1.3 min |
| 20 GB | ~2.2 h | ~53 min | ~27 min | ~5 min |
| 50 GB | ~5.6 h | ~2.2 h | ~67 min | ~13 min |
| 100 GB | ~11 h | ~4.4 h | ~2.2 h | ~27 min |
| 500 GB | ~2.3 days | ~22 h | ~11 h | ~2.2 h |

Real transfers run somewhat slower than these figures because of protocol overhead, disk
speed and, on restrictive networks, a relay hop. One link can be opened by several recipients; each downloads directly from the sender. If three people
download at the same time, they share your upload, so each gets about a third of it.

To find your upload speed, run any internet speed test and look at the **upload** number —
on many home connections it is far lower than the download number.

## How do I keep Windows awake during a transfer?

1. **Plug in the laptop.** Battery-saving modes are more aggressive about sleep.
2. Open **Settings → System → Power & battery → Screen and sleep** (on recent Windows 11
   builds, *Screen, sleep & hibernate timeouts*; on Windows 10, **Settings → System → Power
   & sleep**) and set **sleep when plugged in** to **Never** for the duration.
3. If you will close the lid, set **Control Panel → Power Options → Choose what closing the
   lid does → When plugged in: Do nothing**. Undo it afterwards.
4. Turning the **screen** off is fine — only **sleep** stops the transfer.
5. Optional: Microsoft's free PowerToys includes **Awake**, a tray tool that keeps the PC
   awake for a set time without changing your power plan.

## How do I keep a Mac awake during a transfer?

1. **Plug in the MacBook.**
2. Open **System Settings → Battery → Options** and turn on **Prevent automatic sleeping on
   power adapter when the display is off**. On a desktop Mac, look under **Energy** (Energy Saver). Menu
   names vary slightly between macOS versions.
3. Or open Terminal and run `caffeinate -i` — the Mac won't idle-sleep until you press
   Ctrl+C. It's built into macOS.
4. Don't close the lid unless the MacBook is connected to power and an external display;
   otherwise it sleeps.

## How do I keep the browser tab active?

- **Don't close the tab** and don't quit the browser until the recipient finishes.
- **Chrome:** Settings → **Performance** → *Always keep these sites active* → **Add** →
  `strongfolder.com`. This stops Memory Saver from deactivating the tab.
- **Edge:** in the performance settings, add the site to the list of sites that should
  never be put to sleep (sleeping tabs).
- **Phones:** keep the page on screen and the phone unlocked; mobile browsers pause pages
  that go to the background. For long sends, use a computer. See
  [PC to phone file transfer](https://help.strongfolder.com/en/guides/pc-to-phone-file-transfer/).
- **Avoid other big uploads** at the same time: cloud backup, photo sync and video calls
  compete for the same upload bandwidth.

[Send files now](https://strongfolder.com)
## How can I plan a long transfer?

- **Agree on a time window** with the recipient — both computers awake, both online.
- **Start before you leave your desk**, not as you walk out: the first minutes show whether
  the connection is direct and how fast it runs.
- **Use a cable** for the sender if possible; Wi-Fi is fine but less stable over hours.
- **Split very large sends** into a few folders. If the connection drops, you only redo
  one batch.
- **Check the recipient's free disk space** first. No size limit set by StrongFolder. The practical limits are free disk space on the recipient's device, connection speed, and how long both devices stay online.
- **Send overnight from a desktop** that stays on anyway, if your upload is slow.

## What can I use when I can't stay online?

P2P is the wrong tool when staying online is impossible. Good alternatives:

| Situation | Better option | Why |
|---|---|---|
| You leave in 10 minutes; file is a few GB | Transfer service (WeTransfer-type) | Upload once, recipient downloads later |
| Recipient downloads tomorrow, other time zone | Cloud drive link | Copy waits on the server |
| Many people need it for weeks | Cloud drive (Google Drive, OneDrive, Dropbox) | Shared access, previews |
| Sensitive files that must stay available | End-to-end encrypted cloud | Stored copy the provider can't read |
| Terabytes, slow upload, same city | External drive | Faster than any upload |
| Always-on machine available (office PC, NAS) | Send from that machine | It stays online for you |

For a fuller comparison see [P2P vs cloud file transfer](https://help.strongfolder.com/en/guides/p2p-vs-cloud-file-transfer/)
and [WeTransfer alternatives](https://help.strongfolder.com/en/compare/wetransfer-alternatives/).

## Summary

The sender stays online because, in P2P, the sender's device is the only copy. That's the
price of no upload, no stored copy and no size cap from the service. Estimate the time from
your upload speed, keep the computer awake and plugged in, keep the tab active — and choose
a cloud link when you can't. More on practical limits on [Limits & requirements](https://help.strongfolder.com/en/limits/).

## FAQ

### Can the recipient download after I close my laptop?

No. The link works while the sender keeps sharing. When the sender clicks Stop Sharing or closes the tab, the files are no longer available. If you need the recipient to download later, use a cloud drive or a transfer service that stores a copy.

### Can I use my computer for other things during a transfer?

Yes. Keep the StrongFolder tab open and the computer awake; you can work in other tabs and apps. Heavy uploads in other apps (cloud backup, video calls) share your upload bandwidth and slow the transfer.

### Does the StrongFolder tab have to stay in the foreground?

On a computer, a tab in the background normally keeps running as long as it is open and the computer is awake. To be safe, add strongfolder.com to Chrome's 'Always keep these sites active' list. On phones, a backgrounded browser is often paused, so keep the page on screen.

### What happens if my connection drops in the middle?

The transfer stops. Plan as if you would have to restart it. For very large folders, sending in a few batches limits how much you would need to repeat.

### How long will my transfer take?

Roughly: size in gigabytes × 8,000 ÷ your upload speed in Mbit/s = seconds. 50 GB at 50 Mbit/s is about 8,000 seconds, a little over two hours. Real transfers run somewhat slower because of overhead.

### Why doesn't StrongFolder just store the file so I can go offline?

Because not storing files is the point: no upload wait, no copy on a server, no size cap from the service. Tools that store a copy already exist — use them when staying online is impossible.