QR File Transfer: Send Offline

Move a file from one phone to another with no Wi-Fi, mobile data, Bluetooth pairing, cable, or cloud account. The sending phone turns your file into animated QR codes. The other phone points its camera at the screen and rebuilds the file. That is the entire transfer.

This is offline file transfer in the strictest sense available on Android: the app does not request the INTERNET permission at all. There is no server to upload to, no account to create, no link to expire, and nothing to leak. What is on the screen is the only copy in motion.

HOW IT WORKS

1. Pick any file on the sending phone — a document, a photo, an audio clip, or a ZIP.
2. A code appears and starts animating. Hold the phone still.
3. On the other phone, open the scanner and point it at the first screen.
4. The file lands in Downloads, ready to open or share.

Both phones need the app installed. Nothing else is required — not a network, a sign-in, or a shared Wi-Fi hotspot.

THE PHONES TALK BACK

A camera misses frames. Every file is sent with Reed-Solomon parity, so missed pieces can be rebuilt rather than re-watched. The receiving phone answers over a near-ultrasonic tone at about 19 kHz to say exactly which pieces it still needs. The sender replays those and nothing else. Most people never hear the tone, and the frequency was chosen to be high so young children are not disturbed by it.

If microphone permission is denied, or the hardware has no near-ultrasound support, the codes simply keep looping until the receiver has everything.

WHAT IT IS GOOD FOR

- Handing a document to someone standing in front of you without it touching a cloud
- Two phones on different networks, or on no network at all
- Airplane mode, hotel captive portals, and guest Wi-Fi that blocks device-to-device communication
- Work phones where Bluetooth sharing and USB file transfer are switched off
- Anywhere the honest answer to "How did that file get here?" has to be "It never left the room."

CONTROLS, IF YOU WANT THEM

- 1, 2, or 4 codes on screen at once
- Light, balanced, or dense codes
- 10, 15, or 30 frames per second, or Auto, which follows the receiving phone's own feedback
- 720p or 1080p scanning, and a torch for dark rooms
- Pause the code mid-transfer and resume when the other phone is ready

WHAT TO KNOW BEFORE YOU INSTALL

- Files up to 8 MB. This is a courier for documents and photos, not video.
- It is deliberate, not instant. A few hundred kilobytes takes a minute or two.
- Every received file is checked against a SHA-256 digest before it is saved, so a file that arrives is the file that was sent.
- Android 11 or newer.

PERMISSIONS

- Camera, to read the codes.
- Microphone, to hear the 19 kHz reply.

That is the complete list. No internet, no storage scanning, no location, no contacts, no ads, no analytics, and no account.