editthisaudio

please, just edit this audio.

npx editthisaudio

Why?

You downloaded a podcast / voice memo / audiobook and you just want to:

• chop a chunk out of the middle
• add a fade in / fade out
• save it back

Audacity is overkill, online editors upload your file to god-knows-where, and the system trim tools never quite do what you want.

So I built a tiny audio editor that runs locally in your browser. Open a file (or two, or twelve), edit, save. No upload. No account. No nothing.

Run it

npx editthisaudio                   # open the editor
npx editthisaudio my-podcast.mp3    # open with a file pre-loaded
npx editthisaudio --port 5000       # custom server port
npx editthisaudio --ui-port 8080    # different port for the UI
npx editthisaudio --no-open         # don't auto-open the browser
npx editthisaudio --help

editthisaudio spins up a tiny local server, serves the editor as a static SPA, and opens your browser. All decoding / processing / encoding happens client-side — your files never leave the machine.

What it does

• Open one or many audio files (multi-select concatenates them on a single timeline)
• Cut / copy / paste / delete (⌘X / ⌘C / ⌘V / Del)
• Drag a selection around the timeline to move that audio
• Add audio at the cursor (multi-select supported)
• Fade in / fade out with a smoothstep curve, on the selection or the first/last 1.5 s
• Save — overwrites the original file in place when the browser supports it (Chromium-based), otherwise prompts for a filename and downloads
• Export as MP3 (96 / 128 / 192 / 256 / 320 kbps) or WAV
• Multi-hour audiobook MP3s work — streaming WASM decode + automatic mono / lower-sample-rate fallback so a 5 h file doesn't OOM your tab

Keyboard

| Keys | Action | |---|---| | Space | Play / Stop | | ⌘A | Select all | | Esc | Clear selection | | ← / → | Nudge playhead 1 s | | Shift+← / → | Nudge 10 s | | Alt+← / → | Nudge 100 ms | | Home / End | Jump to start / end | | ⌘X / ⌘C / ⌘V | Cut / Copy / Paste | | Del / Backspace | Delete selection | | ⌘Z / ⌘⇧Z | Undo / Redo | | ⌘scroll | Zoom around the cursor |

Supported formats

In: mp3, m4a, mp4, aac, wav, ogg, flac, opus, webm (anything the browser's native decoder accepts, plus our streaming MP3 decoder).

Out: mp3 (lamejs), wav (16-bit PCM).

Requirements

Nothing exotic — no ffmpeg, no Python, no native bindings, no system libraries. All audio work happens in the browser.

You only need:

| What | Version | For | |---|---|---| | Node.js | ≥ 18 | the editthisaudio CLI server | | A modern browser | Chromium 110+ / Firefox 115+ / Safari 17.4+ | the editor itself (uses OfflineAudioContext in workers, resizable ArrayBuffer, web workers, file APIs) |

For save-in-place (overwriting the file you opened directly on disk), you need a Chromium-based browser — that's the only family with the File System Access API. Firefox and Safari fall back to a download via the modal "Save as" prompt.

What's under the hood

| Job | Implementation | Where it runs | |---|---|---| | MP3 decode (streaming) | mpg123-decoder (WASM) | browser, web worker | | MP3 encode | @breezystack/lamejs (pure JS) | browser, main thread | | Decode m4a / mp4 / aac / ogg / flac / opus / webm | OfflineAudioContext.decodeAudioData() | browser, web worker | | Slice / fade / paste / WAV encode | hand-written, Web Audio API | browser | | CLI server | express + chalk + figlet + open | Node |

Tech stack

| Layer | Tech | |---|---| | UI | React 18 + TypeScript + Vite | | Audio | Web Audio API + Web Workers | | MP3 codec | mpg123 (decode) · LAME (encode) — both compiled / ported to JS | | Fonts | Inter, Fira Code | | CLI | Node + Express |

Build from source

git clone <this-repo>
cd editthisaudio
npm install
npm run dev      # vite dev server with HMR (no CLI involved)
npm run build    # build dist/ for production / npx
npm start        # run the CLI against the built dist/

License

MIT — do whatever you want with it.

go on, just edit that audio. ✌️

youtube.com/ligeiro