unprovable

unprovable / ShadowCat

Public

Single file optical file transfer using a browser

283
21
100% credibility
Found May 27, 2026 at 283 stars -- GitGems finds repos before they trend. Get early access to the next one.
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AI Analysis
HTML
AI Summary

ShadowCat is a single-page web app that transfers files between devices using QR codes as the carrier. It's specifically designed for old phones whose wireless radios (Bluetooth, NFC) no longer work but whose cameras still function. The sender picks a file and the app displays animated QR codes cycling through at a chosen speed. The receiver points their camera at the screen, and the app collects each piece, shows progress, and reassembles the file once complete. It includes optional compression to speed up transfers and verifies everything arrived correctly using checksums.

How It Works

1
📱 Discovering an old phone with dead wireless

You find an old phone in a drawer. The Bluetooth and NFC are broken, but the camera still works.

2
💡 Learning about QR code transfer

You hear about ShadowCat, a tool that uses the camera to move files between devices by displaying and scanning QR codes.

3
📤 Preparing your file to send

On your main computer, you pick the file you want to send and open the web app.

4
🔄 Watching animated QR codes appear

The app splits your file into tiny pieces and displays them as a movie of QR codes, cycling through at your chosen speed.

5
Two ways to scan the codes
📸
Live camera scanning

The old phone scans the QR codes in real-time while they animate on your screen.

🎥
Video recording method

You record a video of the QR codes, then scan the video frame by frame on the old phone.

6
📊 Watching progress as pieces arrive

The receiving app shows a grid of squares filling in as each piece of your file arrives, so you know exactly what's missing.

✅ File arrives complete and verified

Once all pieces are collected, the app checks everything is correct and saves your file to the old phone.

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Star Growth

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AI-Generated Review

What is ShadowCat?

ShadowCat is a single-page HTML tool that transfers files between two devices by encoding them as a sequence of QR codes. Point one device's camera at the other's screen, and the file reconstructs itself on the receiving end. It was built for older phones whose Bluetooth and NFC have died but whose cameras still work. The tool handles chunking, optional gzip compression, CRC verification, and a visual grid showing which chunks are still missing.

Why is it gaining traction?

The niche is specific but real: legacy hardware with dead radios. Instead of buying new hardware, you can move files using just a browser and a camera. The protocol is well-documented, with a reference implementation in Python that mirrors the JavaScript logic. Both sides run tests against shared fixtures, so drift is visible immediately. You can also generate static QR frames from the command line and play them back as an animated GIF.

Who should use this?

- IT folks managing old devices in the field who need to move files without network access - Security researchers requiring air-gapped transfers - Developers who want to understand or extend the QRX1 protocol for custom use cases

Verdict

ShadowCat solves a genuine problem with a clean, self-contained solution. At 283 stars and a 1.0% credibility score, it's a niche project with solid fundamentals but limited community backing. The protocol is well-specified, tests exist on both sides, and the docs cover edge cases like compression fallback and ECC tuning. If you need QR-based file transfer for offline or legacy hardware, this is worth a look. Just expect a smaller community and fewer third-party integrations than you'd find in more mainstream tools.

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