I built BPM Finder, a comprehensive audio analysis toolkit that provides three professional-grade tools: BPM detection, musical key identification, and tempo adjustment all running entirely in your browser.

## What makes it different:

*Privacy-first approach*: Your audio files never leave your device. All processing happens client-side using Web Audio API, rubberband-wasm, and advanced algorithms.

*Three powerful tools in one*: - *BPM Finder*: Dual-algorithm analysis with 99.5% accuracy and confidence scoring - *Key Finder*: Chroma analysis with correlation matrices for precise key detection - *Tempo Change*: Adjust audio speed without pitch changes using professional rubberband algorithm

*Multiple analysis modes*: - Single file analysis with detailed results - Batch processing (up to 50 files simultaneously) - Real-time tap tempo for live BPM detection

## Technical highlights:

- Built with Next.js 15, TypeScript, and Web Workers for intensive processing - Supports MP3, WAV, FLAC, AAC, OGG, M4A (up to 50MB each) - No registration required, completely free to use - Export results to CSV or integrate with DAW/DJ software

## Real-world use cases:

Professional DJs use it for beatmatching in live sets, music producers organize sample libraries by BPM, fitness instructors create tempo-matched workout playlists, and video editors sync background music to cuts.

The project started when I needed reliable BPM detection for my own music production work but couldn't find tools that were both accurate and privacy-respecting. After months of research into audio analysis algorithms and Web Audio API optimization, I built this comprehensive solution.

*Try it*: https://bpm-finder.net/

Would love feedback from the HN community, especially from fellow musicians, developers working with audio processing, or anyone who's tackled similar browser-based analysis challenges.

*Tech stack*: Next.js, TypeScript, Web Audio API, rubberband-wasm, web-audio-beat-detector, Tailwind CSS

Show HN: BPM Finder: Advanced Audio Analysis Toolkit