Code to QR Code

Transfer files via animated QR codes. No network, no Bluetooth, no USB — just a screen and a camera.

Try it live

How it works

1. Encode — Drop a file or folder. It's compressed, split into chunks, and displayed as animated QR codes.
2. Transfer — Point a phone camera at the screen, or export a GIF/video and send it any way you like.
3. Decode — Open the decoder on the receiving device. Scan with the camera or upload the GIF/video. The file is reassembled.

Quick start

npm start

Opens an HTTPS server (auto-generated self-signed cert) at https://localhost:3000. Your browser will warn about the cert — click Advanced → Proceed.

Without Node

Open encoder/index.html or decoder/index.html directly in a browser. Camera decoding requires HTTPS so it won't work over file://, but GIF/video upload decoding works fine.

Features

Encoding:

• Multi-file and folder support (auto-zipped)
• Gzip compression
• GIF, MP4, and WebM export
• Reed-Solomon erasure coding (+2/+5/+10 parity chunks)
• Adjustable chunk size (100–800 B) and QR error correction level (L/M/Q/H)

Decoding:

• Live camera scan with native BarcodeDetector (hardware-accelerated) + jsQR fallback
• GIF and video upload decoding
• Progressive preview as chunks arrive
• RS recovery of missing chunks
• ZIP archive browsing

Project structure

index.html              Landing page
encoder/index.html      Encoder (self-contained)
decoder/index.html      Decoder (self-contained)
shared/reedsolomon.js   Reed-Solomon library (source)
server.js               HTTPS dev server
test/test.js            Test suite (43 tests)

Encoder and decoder pages bundle all dependencies locally — no CDN, no build step. They work from file://, GitHub Pages, or the dev server.

Chunk protocol (v2)

Each QR code contains a JSON chunk:

{
  "v": 2, "i": 0, "n": 17,
  "hash": "a1b2c3d4", "name": "file.txt",
  "gz": 1, "zip": 0, "rs": 1, "k": 7, "sz": 19721,
  "t": "d", "d": "base64data..."
}

Field	Description
v	Protocol version (2)
i	Chunk index (0-based)
n	Total chunks (data + parity)
hash	FNV-1a hash of original file
name	File name
gz	1 if gzip-compressed
zip	1 if zip archive
rs	1 if Reed-Solomon enabled
k	Data chunk count (for RS)
sz	Original file size in bytes
t	d = data, p = parity
d	Base64 payload

Testing

npm test

43 tests covering GF(256) arithmetic, Reed-Solomon encode/decode, recovery scenarios, path traversal protection, GIF parser bounds checking, and the full encode→RS→recover→decompress pipeline.

Camera tips

• Fast scanning: chunk size 300 + EC level L = larger cells, easier to scan
• Fewer frames: chunk size 800 + EC level M = fewer QR codes in the sequence
• Missed chunks: add +2 or +5 RS parity to recover from dropped frames
• Encoder FPS: start at 3–6 FPS and adjust

Requirements

• Node.js (for dev server and tests)
• Chrome recommended (BarcodeDetector API support)
• OpenSSL optional (server falls back to JS cert generation)

License

MIT