# IO Transfer — full brief for AI agents

> Screen-to-camera file and text transfer using fountain-coded animated QR codes. No network path between devices.

## What it is

IO Transfer (https://iotransfer.com/) is a free progressive web app. A sender page turns a file or pasted text into a continuous stream of QR frames. A receiver page uses the device camera to recover the payload, verify SHA-256, then offer Save (files) or Copy (text).

Brand: IO Transfer · Site: https://iotransfer.com/ · Copyright © 2026 IO Transfer Ltd.

## What it is not

- Not a messaging app, cloud drive, or peer-to-peer network transfer
- Not encrypted by default — any camera aimed at the sender screen can read the stream
- Not an installable native store app (optional Add to Home Screen / PWA)

## Core facts

- Channel: light only (screen → camera)
- No account, pairing codes, or server-mediated transfer path between the two devices
- Works offline after first visit (service worker caches the app, never transferred content)
- Files up to 64 MB; text snippets supported
- Filename and media type preserved; gzip when helpful
- Optional matching passphrases encrypt the fountain payload (AES-GCM)
- Session check codes help confirm both devices locked onto the same stream
- Camera API requires a secure context (HTTPS)

## How to use (quick start)

1. Open https://iotransfer.com/ on both devices.
2. Sender: open Send, choose a file (or Text). Raise screen brightness fully. QR stream starts.
3. Receiver: open Receive, Start camera, fill the viewfinder with the code; prop the phone to reduce focus hunting.
4. When progress completes, Save the file (after SHA-256) or Copy the text.

Sender deep link: https://iotransfer.com/send  
Receiver deep link: https://iotransfer.com/receive

## Privacy summary

Nothing is transmitted anywhere except as light. There is no account, no pairing, no analytics, and no network path between the devices for the transfer itself. Without a passphrase the property is *no network*, not secrecy. Received text is not persisted; saved files go to the browser download location. Staged received media in Cache API is cleared on hide, TTL, next transfer, or Clear cache.

## Troubleshooting (high signal)

- Lower sender bytes/frame and tx fps if the receiver sees nothing
- Fill the camera frame; avoid hand tremor / autofocus hunting
- On multi-lens phones pick wide / main rear lens, not telephoto
- Max brightness on the sending screen

## Primary URLs

- https://iotransfer.com/
- https://iotransfer.com/send
- https://iotransfer.com/receive
- https://iotransfer.com/llms.txt
- https://iotransfer.com/sitemap.xml

## Source & docs

Repository: https://github.com/cubbysoftware/iotransfer  

User docs: docs/user/ · Technical docs: docs/technical/