ShadowCat – file transfer through QR Codes in a Browser

In plain words

ShadowCat is a file transfer tool that works directly in web browsers using QR codes. Users can share files by generating a QR code, which another person scans to receive the transfer. The tool operates without requiring installation of additional software or accounts. It is designed for anyone needing a quick, simple way to move files between devices locally through a browser interface.

written from the facts on this page · September 2026

From the sources

A fully offline, single-file HTML page for moving data between two devices via QR codes — intended for old phones whose radios (BLE, NFC, etc.) are dead but whose cameras and browsers still work. See SPEC.md for the full wire format, frame diagrams, and invariants. A reference encoder and decoder live in tools/ : pip install qrcode[pil] pyzbar pillow opencv-python python tools/qrx1_encode.py myfile.bin --out frames/ python tools/qrx1_encode.py myfile.bin --gzip --out frames/ # gzip the payload python tools/qrx1_decode.py frames/ -o out/ Tests Both sides assert against a shared golden fixture (known input bytes → known CRC and header). If the JS or Python implementation drifts from the spec,…from github.com

• PT
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