Installing Subtl and granting the two permissions
Subtl is a normal macOS application: a signed, notarised .dmg, no kernel extension, no meeting plugin, nothing installed into Zoom or Teams. What it does need is permission to hear the call.
What you need
macOS 13 (Ventura) or newer, on Apple silicon or Intel. About 300 MB of free space for the app, and another 1–2 GB if you later turn on recognition on your own machine.
Headphones are not required, but they make a real difference: without them your microphone hears the other person through the speakers, and the two sides of the conversation blur into one.
Install it
Four steps, and the fourth is the one people forget.
- 01Download the .dmg and open it.
- 02Drag Subtl into Applications. Opening it from the mounted disk image works, but macOS will keep asking about permissions every time.
- 03Open Subtl. The first launch takes a few seconds longer while macOS verifies the notarisation.
- 04Sign in with your email. A six-digit code arrives; there is no password to invent.
Give it the two permissions
Subtl asks for exactly two things, and the onboarding walks you through both. Microphone is how it hears you. System audio recording is how it hears everyone else — it is the permission macOS uses for screen and audio capture, and the call apps themselves ask for the same one.
If you clicked past a prompt, open System Settings → Privacy & Security and switch Subtl on under Microphone and under Screen & System Audio Recording. macOS requires the app to be restarted after the second one; Subtl will say so.
Check that it can actually hear
On the start screen there is a sound test: it plays a short chime through your speakers and tells you whether it heard it back on the system-audio channel. If that test passes, a real call will work.
If it fails, the usual cause is that the permission was granted but the app was not restarted, or that the output device in the Audio card is not the device your call actually uses.
Read next
- Your first callStart a session, pick the two languages, and read the transcript and its translation while you talk. What appears on screen, when, and what the other side sees.
- Recognition on your MacRun speech recognition entirely on your own Mac with Whisper: nothing about the call leaves the device. Which model to download, which Macs are fast enough, and what you give up.