FnKey

FnKey is a lightweight macOS menu‑bar utility written in Rust that enables push‑to‑talk voice input. When the user holds the Fn key, the app activates the microphone, streams audio to a transcription service, and on release automatically pastes the transcribed text into the active window. The interface shows a simple idle/recording icon and offers optional automatic Return keystroke after pasting.

The software supports two back‑ends: Deepgram Nova‑3 for low‑latency streaming transcription and Groq Whisper as a batch fallback when a Deepgram key is not provided. It includes basic audio preprocessing, automatic sample‑rate handling, and a menu option to edit custom keyword lists that improve recognition of domain‑specific terms.

FnKey is open‑source and distributed as a free‑tier, stable macOS application. Installation requires downloading the appropriate binary, placing it in the Applications folder, and supplying API keys for the chosen transcription service. Permissions for input monitoring, microphone, and accessibility are requested to enable key detection and auto‑pasting.