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.
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.
Straight to a page: send · receive
Any file — up to 64 MB in a single stream, larger files split into verified segments — 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. Expect hundreds of KB/s screen to camera, depending on the two devices and the light.
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.
This is an extended fork of bashalarmistalt/decimen-optical-transfer.
Segmented large-file transfer. One stream numbers its source blocks in 16 bits, so a big file cannot fit in a single stream however the size limit is set. Above 64 MB the sender now splits the file into segments of at most 16 MiB and streams them in turn, cycling until the receiver has them all. Each segment carries its own SHA-256 plus the hash of the whole file; the receiver verifies every segment as it lands, tolerates any arrival order, ignores repeats, and verifies the reassembled file before offering it. Segments gzip on the same terms as a single-stream file. Details in protocol.
The fork also drops the upstream project's CLA, funding config, release workflow, demo mode and benchmark rig — none of which apply here. It publishes no benchmark records of its own, so the speed figures above are deliberately unquantified.
Using it — quick start · sending · receiving · troubleshooting · install & offline · privacy
How it's built — architecture · protocol · platform quirks · build & deploy · diagnostics
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.
npm install
npm run dev # https dev server with HMR
npm run serve # build, then serve the production bundle
npm run diagnostics # dev server + per-transfer run reports in the terminal
npm test # golden wire-format vectors and unit tests
npm run build # the hosted site → dist/
npm run build:standalone # both self-contained pages → dist-standalone/
npm run build:all # everythingOpen https://localhost:5173/send/ on the sending device and the printed
Network URL on the receiving phone (accept the self-signed certificate
once). Walkthrough: quick start.
.github/workflows/pages.yml publishes dist/ to GitHub Pages on every push
to main. It passes the deployment's own address in as VITE_SITE_URL, so
the canonical links, social-card URLs and — the one that actually matters —
the sender's share receiver link all point at this site rather than
anywhere else. Building without that variable falls back to the same URL, so a
local build advertises the same place a deployed one does.
The site builds with base: "./" and therefore works under a project subpath
with no configuration.
The concept here was arrived at independently by the original author. It turns out several people have had similar ideas, and their takes are all worth a look:
- mohankumarelec/airgapped-qr-code-transfer: browser-based QR file transfer with compression and sequential chunking.
- divan/txqr (2018): animated QR plus fountain codes in Go, with two excellent write-ups on why fountain coding beats sequential looping.
- sz3/libcimbar: goes past QR entirely with a custom high-density color code purpose-built for this channel.
Originally built by Evan Crawley (Bash Alarmist), with node-qrcode and decimen-codec, a custom zxing-cpp build. This fork is maintained by pythonIsFast.
AGPL-3.0-or-later, as of v0.4.0. Releases up to and including v0.3.0 were MIT-licensed and remain available under those terms.
Because this is the AGPL and not the GPL, running the software over a network counts: anyone who uses the site above is entitled to the source of the exact version serving them, which is what this repository is.
Portions were contributed under MIT, and the vendored decimen-codec decoder (AGPL-3.0-or-later) incorporates zxing-cpp under Apache-2.0 — see NOTICE.