README

Decimen Optical Transfer: fountain-coded QR file transfer

Send a file between two devices using nothing but a screen and a camera.
One page displays the file as an endless stream of animated QR codes; another
device points its camera at it and reconstructs the file. No network path
between the devices, no app, no pairing, no permissions beyond the camera.
The payload travels as light.

 Try it

 → decimen.app

Open it on both devices and go — nothing to install. Works offline after the
first visit, and installs as an app on both iOS and Android if you want it on
a home screen.

Files up to 64 MB (or a pasted text snippet), filename and media type
preserved, gzip only when it helps, SHA-256 verified before anything is
offered — and received video plays right in the page. A stream can also be
exported as a looping animation
(APNG, or a PNG sequence for video editors): any camera pointed at the file
playing — in a page, a stream, a video lesson — receives it like the live
sender. The interface speaks
twelve languages (English, español, português, français, Deutsch, italiano,
русский, हिन्दी, 简体中文, 日本語, 한국어, العربية — with right-to-left
layout where it belongs); machine-drafted translations say so on the page
until a native speaker has reviewed them. Currently measured at
418.5 KB/s sustained screen to
camera — records with receipts.


  

Mid-transfer: a phone pulling a file out of the air at 130 KB/s.

Neither mode is encrypted: whatever is on the sending screen is readable by
any camera pointed at it. The property this gives you is no network, not
confidentiality — see privacy.

 Measured speed


!sustained record

One record run per device pair. Sustained is whole-transfer goodput;
peak is the best ≥1 s window inside that same run. Every row links to
the full diagnostics run report that produced it
(how these are measured).

| pair | sustained | peak | transfer | codes | devices | when | receipt |
|---|---|---|---|---|---|---|---|
| desktop → phone | 418.5 KB/s | 601.5 KB/s | 1.0 MB in 2.5 s | 4 | Odyssey G9 49″ → iPhone 17 Pro Max | 2026-08-09 (v0.4.0) | run |
| phone → phone | 199.2 KB/s | 340.8 KB/s | 1.0 MB in 5.1 s | 2 | iPhone 17 Pro Max → iPhone 17 Pro Max | 2026-08-09 (v0.4.0) | run |


 Documentation

Using it — quick start ·
sending · receiving ·
troubleshooting ·
install & offline ·
privacy

How it's built — architecture ·
protocol ·
platform quirks ·
build & release ·
localization

The short version of the protocol: a screen-to-camera link has no
back-channel, so the sender streams fountain-coded frames (Luby
transform) — the receiver
collects any ~K·1.15 distinct frames in any order and peels the file out.
Dropped frames cost time, never correctness.

 Run it yourself

bash
npm install
npm run dev                https dev server with HMR
npm run serve              build, then serve the production bundle
npm run demo               demo mode: only the bundled payloads can be sent
npm run diagnostics        dev server + per-transfer ru