What is this tool?
Camera File Transfer sends a file from one device's screen to another device's camera, with no Wi-Fi, Bluetooth, cable or internet connection. The sending device shows the file as a fast stream of QR codes; the receiving device films them and rebuilds the file. The codes use a fountain code, so the camera can miss frames and catch them in any order: the file is complete as soon as slightly more codes than its size have been read, and its SHA-256 checksum is verified at the end. It works between any phone, computer, tablet or TV with a browser and a camera, and once the page has loaded it works offline, which makes it useful for air-gapped computers and for devices that will not pair. It is slower than Wi-Fi (typically 5 to 50 KB per second, depending on code density, codes on screen and the camera), so it suits documents, text, photos and files up to a few megabytes.
How to Use
- On the device that has the file, open Send a file and choose the file.
- On the other device, open the same page and tap Receive a file, or scan the link code with its camera app.
- Press Start sending, then Start camera on the receiving device and point it at the codes so they fill most of the view.
- Keep both devices steady until the receiver shows the file as received and verified.
- Tap Save file. Raise the density or show 2 or 4 codes at once on a large screen to go faster.
Frequently Asked Questions
Does it use the internet or Wi-Fi?
No. The file only travels as light from one screen to the other camera. Nothing is uploaded, and after the page has loaded once it works with networking turned off.
How fast is it?
Typically 5 to 50 KB per second: a 1 MB photo takes from about 20 seconds to a few minutes. Dense codes, 2 or 4 codes on a large screen and a good camera are fastest; small phone screens and far-away cameras need the Easy to read setting.
What if the camera misses some codes?
It does not matter. The codes are a fountain code: any set of codes slightly larger than the file rebuilds it, in any order, so the sender keeps showing new codes until the receiver has enough.
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