"No file size limit" is one of the first things we say about StrongFolder, and it is true. It is also the kind of claim that deserves fine print, so this post is the fine print. We don't cap your files. Your connection, your disk and your patience still do — and it helps to know how much before you start a 200 GB transfer at 6 pm on a Friday.
Why do most transfer services have a size limit?
Because they store your file. A transfer service receives the upload, keeps it on its servers for days and serves it to every recipient. Every gigabyte costs it storage and bandwidth, so free plans are capped — often at a few gigabytes per transfer — and bigger sends move to paid plans. That is a fair business model for a locker.
StrongFolder is not a locker. Files go directly from your browser to the recipient's and are never stored on our servers. A 1 TB file costs us no more storage than a 1 MB one: zero. So we have no reason to cap it. 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.
So what does limit a transfer?
Three things, none of them set by us.
1. Your upload speed. A direct transfer can't go faster than the sender's upload or the recipient's download, whichever is slower. Many home connections upload much slower than they download, so your upload is usually the bottleneck. Check it with any speed test before a big send.
2. The recipient's free disk space. The files are written straight to their disk. A 300 GB folder needs 300 GB free, plus some headroom. One classic trap: a USB stick formatted as FAT32 cannot hold a single file larger than 4 GB, however much space it has.
3. Time online. 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. If your laptop sleeps, the transfer stops. The same applies to the recipient. A transfer of many hours needs two devices that stay awake for many hours.
How long will my transfer take?
Here is the formula I use: size in GB × 8,000 ÷ upload speed in Mbit/s = seconds. One gigabyte is 8,000 megabits, so you divide by how many megabits per second you can push.
| Size | 10 Mbit/s | 50 Mbit/s | 100 Mbit/s | 500 Mbit/s |
|---|---|---|---|---|
| 10 GB | ~2.2 h | ~27 min | ~13 min | ~3 min |
| 50 GB | ~11 h | ~2.2 h | ~67 min | ~13 min |
| 100 GB | ~22 h | ~4.4 h | ~2.2 h | ~27 min |
| 500 GB | ~4.6 days | ~22 h | ~11 h | ~2.2 h |
| 1 TB | ~9.3 days | ~44 h | ~22 h | ~4.4 h |
Real transfers add roughly 5–15 % for protocol overhead. The table assumes the recipient's download is at least as fast as your upload.
Look at the left column for a moment. At 10 Mbit/s, 100 GB is almost a full day, and 1 TB is more than a week. "No limit" is true there too, but a week of uninterrupted uptime on both ends is not a realistic plan. Which brings me to the honest part.
When is no file size limit not enough?
When the time column is longer than the time both of you can stay online. In that case, other tools are better, and I'd rather say so:
- You can't keep your computer on. Upload to a cloud drive overnight and send a link; the recipient downloads whenever they like. Why the sender stays online explains the trade-off.
- It's terabytes over a slow line. Copy it to an external SSD and hand it over or post it. Copying 1 TB to a fast drive takes far less time than pushing it through a 10 Mbit/s upload.
- You send the same huge file every week. A paid cloud or transfer plan may simply be more convenient. Check the vendor's current pricing.
For everything between "too big for email" and "too big for your connection", a direct transfer is usually the fastest free route, because the recipient downloads while you send instead of waiting for a full upload first.
How do I make a big transfer actually finish?
Most failed large transfers I see fail for boring reasons. This checklist prevents nearly all of them:
- Disable sleep on both computers and keep laptops on power.
- Use a cable instead of Wi-Fi if you can; it is steadier over hours.
- Pause other uploads — cloud backup, photo sync, video calls. They compete for the same upload.
- Check the recipient's free space and file system before you start.
- Keep the StrongFolder tab open, and on a phone keep it on screen: phones pause background tabs.
- Serve big recipients one at a time. One link can be opened by several recipients; each downloads directly from the sender. Your upload is split between them.
- Start early. At 50 Mbit/s, a 100 GB send started at 9 am is done by early afternoon; started at 6 pm, it runs until late in the evening.
If the connection drops, the recipient starts the download again from the same link while you are still sharing — another reason to get the setup right before a long transfer.
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What should you read next?
For the full list of browsers, requirements and practical limits, see Limits & requirements. If you are planning one very large send, our guide on how to send a 100 GB file for free compares free services and walks through the setup. For video in particular, see how to send large video files.
"No file size limit" is a promise about what we won't do: we won't cap you. The rest is arithmetic — and now you have the table. If your numbers look odd in practice, write to me at info@strongfolder.com.