What is NullKit?
NullKit is a growing collection of free, browser-based tools built for everyday needs. Whether you're practicing card games, testing your hardware, analyzing data files, or tuning instruments — we've got a lightweight tool that works right in your browser.
Every tool is designed with the same philosophy: fast, free, and private. Your data never leaves your device. No accounts needed. Just open and use.
Our Tools
掼蛋练习 (Guandan Trainer)
The first dedicated practice tool for Guandan (掼蛋), China's most popular card game with over 1.4 billion players. Features include:
- 30+ curated puzzles — beginner to advanced, each teaching a specific strategy
- AI opponents — 3 difficulty levels with real-time move scoring
- Smart hints — AI analyzes your hand and suggests optimal plays with explanations
- Tutorial — 7-page guide from rules to advanced tactics
ChoirPitch — Pitch Pipe for Singers
A clean, fast pitch pipe designed for choir directors, a cappella groups, barbershop quartets, and solo singers. Built because existing apps are either abandoned or full of ads.
- Full chromatic range — C2 through C7
- Setlist management — save starting pitches for each song
- Custom tuning — A4 = 432Hz, 440Hz, 415Hz, or any custom frequency
- Works offline — install as PWA for rehearsals without internet
FileScope — Data File Profiler
Instant data profiling for Parquet and Lance files. Drag and drop any columnar file to get a complete statistical overview — powered by DuckDB running in WebAssembly.
- Column statistics — min, max, mean, median, nulls, uniques
- Distribution charts — histograms for every column
- Correlation heatmap — Pearson matrix for numeric columns
- 100% client-side — your data never leaves the browser
DeviceTest — Hardware Testing Suite
A comprehensive set of 12+ browser-based hardware tests. Check if your microphone, webcam, speakers, keyboard, and screen are working properly — no software to install.
- Mic test — real-time audio levels and waveform
- Speaker cleaner — eject water with sound waves
- Dead pixel test — full-screen color check
- CPU & GPU benchmarks — WebAssembly and WebGL performance
Why Browser-Based?
🔒 Privacy First
Everything runs locally in your browser. We don't collect, upload, or store any of your data. What happens on your device stays on your device.
⚡ Instant Access
No app store downloads, no installations, no updates to wait for. Open the URL and start using the tool immediately on any device.
📱 Works Everywhere
Desktop, laptop, tablet, phone — if it has a modern browser, it works. Responsive design adapts to any screen size.
💰 Actually Free
No freemium walls, no "sign up to continue", no feature limits. Every tool is fully functional with zero cost.