heu

Hold fn, talk, let go. The words land wherever your cursor is.

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heu is a dictation app that lives in your menu bar. It runs Whisper locally on your GPU, so your audio never leaves the machine — there's no account, no server, and nothing to sign into.

It's deliberately small. The whole app is a 3.2 MB native binary; no Electron, no bundled browser. It sits in the menu bar all day without you noticing it.

Supported versions

macOS	Status
26 Tahoe	Tested — this is what heu is developed on
15 Sequoia	Should work, not actively tested
14 Sonoma	Minimum supported, not actively tested
13 Ventura and earlier	Not supported — the app won't launch

Apple Silicon only. The binary is arm64-only, so Intel Macs can't run it at all, regardless of macOS version.

The floor is macOS 14 because that's the deployment target the app is built against (LSMinimumSystemVersion in src/Info.plist). On macOS 13 the installer refuses outright rather than failing at runtime. If you run heu on 14 or 15, I'd genuinely like to know whether it worked — open an issue either way.

You'll also need a whisper.cpp ggml-*.bin model; heu can download one for you on first launch. Building from source additionally needs Xcode Command Line Tools and CMake 3.16+.

Install

heu is ad-hoc signed, not notarized — I'm not paying Apple $99/year to give away a 3 MB app. That costs you one extra step on the download path, and nothing at all if you build it yourself.

Build it yourself

git clone https://github.com/ggerganov/whisper.cpp
git clone https://github.com/pirate329/heu
cd heu
cmake -B build -S .
cmake --build build -j$(sysctl -n hw.logicalcpu)
bash scripts/package.sh
cp -R dist/heu.app /Applications/

No Gatekeeper prompts on this path. macOS only blocks apps carrying a com.apple.quarantine flag, and that flag is attached by whatever downloaded the file — your browser. A binary you compiled locally never has it. You also get to read the source first, which is rather the point of an app that claims your audio never leaves the machine.

Takes about a minute on an M-series Mac. Needs Xcode Command Line Tools and CMake 3.16+. The build expects whisper.cpp as a sibling of this repo, which is what those two clones give you:

.
├── heu/          ← this repo
└── whisper.cpp/

Or download the DMG

Grab it from the latest release, drag heu into Applications, then run:

xattr -dr com.apple.quarantine /Applications/heu.app

That removes the download flag your browser attached, and heu opens normally from then on. Only do this for software you're willing to trust — in this case the thing you're allowing is the repo you're reading.

If you'd rather not touch the Terminal: double-click heu, click Done on the warning, then open System Settings → Privacy & Security, scroll to the Security section, and click Open Anyway next to the message about heu. The button is only offered for a short window after the failed launch, so do it right away.

Note: the old right-click → Open trick no longer works. Apple removed that bypass in macOS 15 Sequoia, so on Sequoia and Tahoe it just shows you the same refusal with no way through.

First launch

heu starts with no model, so it opens Settings and offers to download one. Pick base.en if you're not sure — it's 148 MB and fast enough to feel instant on any Apple Silicon Mac.

Permissions

macOS will ask for three things. heu needs all of them, and the second one is the one people get stuck on:

Permission	Why
Microphone	To hear you.
Accessibility	To find the focused text field and write into it.
Automation	For the Cmd+V fallback when a field won't accept direct insertion.

If transcription works but no text appears, it's Accessibility. Open System Settings → Privacy & Security → Accessibility, make sure heu is toggled on, then quit and relaunch heu — macOS only re-reads that permission at startup, so the toggle alone does nothing until you restart the app.

Using it

Hold fn and speak. Release when you're done. A pill appears in the menu bar while it's listening, and the text is inserted at your cursor a moment after you let go.

There's also a wake word — say "hey heu" and it starts listening without the keypress. Handy when your hands aren't on the keyboard.

fn is used because it's the one key on a Mac that isn't already spoken for. It doesn't collide with anything in the app you're typing into.

Models

heu reads any whisper.cpp ggml-*.bin from:

~/Library/Application Support/heu/models/

Settings can download them for you, or you can drop one in yourself and it'll be picked up. Larger models are more accurate and slower:

Model	Size	Notes
ggml-tiny.en.bin	75 MB	Fastest, noticeably rougher
ggml-base.en.bin	148 MB	Good default
ggml-small.en.bin	488 MB	Better with accents and proper nouns
ggml-medium.en.bin	1.5 GB	Slower, diminishing returns for dictation

The .en variants are English-only and beat the multilingual ones of the same size at English. Drop the suffix if you need other languages.

Development

Build it as described in Install, then run it straight out of the build directory:

./build/heu -m ~/Library/Application\ Support/heu/models/ggml-base.en.bin

Omit -m and it'll hunt for a model in the usual places. -ng disables Metal if you want to compare against CPU inference.

Note that the dev binary at build/heu needs its own Accessibility grant — macOS ties that permission to the executable, so the one you gave /Applications/heu.app doesn't carry over.

To produce a signed app bundle and a DMG:

bash scripts/package.sh

How it works

Audio comes in through miniaudio at 16 kHz mono into a ring buffer. A background thread watches the buffer's RMS against a rolling noise floor, and when it crosses the threshold it hands a window to whisper.cpp running on Metal. Transcribed text goes to the Accessibility API, which writes directly into the focused element; if that element refuses, heu falls back to putting the text on the clipboard and sending Cmd+V.

src/
  App/       Entry point, Cocoa run loop, menu bar wiring
  Engine/    Audio capture, ring buffer, VAD, whisper inference
  Input/     fn key event tap, text insertion
  HUD/       Listening overlay and wave animation
  Model/     Model catalog, downloads, hot-switching
  UI/        Menu bar pill and the Settings panel

The only network code in the app is the model downloader in src/Model/ModelManager.mm, which fetches .bin files from Hugging Face. Audio is never sent anywhere — you can verify that by grepping the source for NSURLSession, which turns up exactly one file.

Troubleshooting

Nothing happens when I hold fn. Check Accessibility, then relaunch. The event tap can't install without it.

It transcribes music or background noise. The wake-word listener runs continuously and will try to transcribe whatever it hears. That's expected — it only inserts text when it matches the wake word or you're holding fn.

It won't launch on my Mac. heu requires macOS 14 (Sonoma) and Apple Silicon. The binary is arm64-only, so Intel Macs can't run it at all.

Transcription is slow. Try a smaller model, and confirm Metal is being used — the startup log prints the GPU it picked.

License

MIT. See LICENSE.

Built on whisper.cpp by Georgi Gerganov, which does the actual hard part.