QR Code File Transfer: How Scanning a Code Sends Your Files

A QR code is nothing but a picture that holds a small amount of text. Your phone camera reads the picture and turns it back into text. In a file transfer, that text is the information two devices need to find each other. Understanding that one idea makes QR transfers easy to trust and easy to use.

What is inside the code

The QR code PeerFlow shows contains a short session code, the same one you could type by hand, packaged so that a camera can read it. It does not contain your file, your name or your password. When the other device reads the code, it knows which session to join. The two devices then set up a direct connection, and the file travels across it.

Why use a QR code at all

Typing a code is fine on a computer, but awkward on a phone, and mistakes are easy: is that an O or a zero? Scanning removes the typing and the mistakes. It is also quicker when the two devices are next to each other, which is the most common case: a phone and a laptop on the same desk.

How a QR transfer works, step by step

1. The sender opens PeerFlow and chooses the files. A session is created and a code is shown as text and as a QR code.
2. The receiver chooses Scan QR (or uses the phone camera) and points it at the sender's screen.
3. The code is read and the receiver's device asks PeerFlow's server to introduce it to the sender's device.
4. The two devices negotiate a direct, encrypted connection. If they are on the same network, it stays on that network.
5. The files stream across. The server is no longer involved in the data.

Scanning from different devices

• Phone to PC: show the QR on the PC screen, scan it with the phone, or the other way round.
• Phone to phone: one phone shows the code, the other scans it. This is quick for sending a video to a friend in the same room.
• PC to PC: use the typed code, since neither has a camera pointed at the other's screen. Laptop webcams can scan too, but typing is usually faster.

Is a QR code safe?

The QR code is as safe as the code under it: it works for one session and connects one receiver. A few sensible habits make it safer still.

• Show the code only to the person you mean to send to. Do not post a screenshot of it in a group chat.
• Check what you scan. Only scan codes shown to you by someone you know. A code from an unknown source could start a session you did not expect.
• Look at the screen. Both devices show the transfer while it runs, so you notice at once if something is not what you expected, and you can close the page to stop it.

For the technical side of the connection, read the page about security.

When scanning does not work

Glare on the screen, a dirty camera or a very small code can stop a scan. Move closer, raise the brightness on the screen that shows the code, or fall back to typing the short code. If the camera permission was refused, allow it in your browser or phone settings; PeerFlow's checklist can show you which permissions are missing.

QR versus typing versus nearby sharing

Beyond files

The same idea of a short code appears in PeerFlow's remote desktop and in meeting links: a small piece of text that introduces two parties and then gets out of the way. If you want to see it in action, install the Android and Windows apps and try a transfer between your phone and your PC.