Neiro

A local-first audio player and visualizer. Drop a file in and it is decoded, equalized and rendered entirely inside the browser tab — no account, no upload, no server. The spectrum you see is the signal you hear.

npm install
npm run dev

Drag audio anywhere onto the page, or use the queue's Add files. Supports MP3, WAV, FLAC, OGG, M4A, Opus and anything else the browser can decode.

• Four visualizer modes — bars, wave, radial and orbit, each rendered on canvas at device pixel ratio.
• Five-band equalizer — shelving and peaking biquads at 60 Hz, 250 Hz, 1 kHz, 4 kHz and 12 kHz, with presets.
• Microphone input — visualize a live source with the output muted, so nothing loops back.
• ID3 tags — a dependency-free parser reads title, artist, album and cover art.
• Media Session — hardware play buttons and lock-screen controls work.
• Adjustable hue — one slider recolors the whole interface and every visualizer.
• Playlists that stick around — when the CLI is serving your library, playlists, play counts and your resume position are saved to disk.

Settings persist to localStorage; audio never does.

<audio> ──► 5× BiquadFilter ──► AnalyserNode ──► GainNode ──► destination
microphone ──────────────────►

The analyser sits after the equalizer, so the bars react to the filters, and before the output gain, so microphone input can be visualized with the speakers silent — no feedback loop.

Play any folder of music in your browser:

npx neiro-cli ~/Music

It indexes the folder, serves the player on localhost and streams files straight off disk with HTTP range support, so seeking is instant. Tracks are addressed by a stable hash rather than a path, and the server binds to 127.0.0.1 by default.

Playlists you make in the player are written to ~/.neiro/library.json, alongside play counts and your last position — so nothing is lost when the process stops. Run it with --daemon and closing the terminal won't stop it:

neiro ~/Music --daemon   # detached; survives closing the terminal
neiro status
neiro stop

See packages/neiro-cli for all options.

The engine is published on its own, framework-agnostic and dependency-free:

npm i neiro-visualizer

import { AudioEngine, Visualizer } from 'neiro-visualizer'

See packages/neiro-visualizer for the API.

The app consumes this package from source via a Vite alias and a tsconfig path, so there is one implementation and no build-order dependency between them.

The marketing site in site/ is a single static file — open it directly, or serve the folder with anything.

React 19 · TypeScript · Vite 8 · Tailwind v4 · Web Audio API · Canvas 2D. No runtime dependencies beyond React.

MIT