The rules
The app summarises these in a Shortcut Guide next to the hotkey field:- Use at least one modifier — Ctrl, Alt, Shift, Cmd, or similar — or a key that types nothing on its own.
- Three keys maximum. Four-key combinations are rejected.
- A letter or digit on its own isn’t allowed. Keys that type nothing — F-keys, arrows, Space, Esc and their neighbours — are accepted alone, and so is the macOS Globe key.
- Reserved system shortcuts are blocked. Each platform has its own list.
- Some combinations may still conflict with whatever else you run — those can’t be predicted, only tried.
The one principle worth knowing
Pick a combination that types nothing. A hotkey is held down while you talk, sometimes for a minute, in whatever app you’re already typing into. If it ever slips through — a moment before the app grabs it, a window that doesn’t give it up — a combination ending in a letter puts that letter in your document. A combination made only of modifier keys can’t. That single test explains why the defaults are what they are, and it’s a better guide than any list.What to use
In every case the default is the recommendation. If dictation is working,
there’s no reason to change it — the reasons to change are a physical conflict
with something you use constantly, a keyboard without the key, or wanting the
same shortcut across two machines with different layouts.
Modifier-only combinations like
Ctrl+Win are fully supported on Windows,
and are what it ships with. On a Mac, use Right Option on its own or add
a regular key; on Linux it depends on your desktop — hotkeys by
platform has the map.What to avoid
Win+Hon Windows — that’s Windows’ own voice typing shortcut. Binding it puts two dictation systems on one key.Cmd+Spaceon macOS — Spotlight, and the default for several popular launchers besides.- Anything ending in a common letter with one modifier —
Ctrl+S,Cmd+Fand their neighbours mean something in nearly every app, and most are blocked outright. - Caps Lock. Some dictation tools use it; OpenWhispr doesn’t support it.
What the errors mean
When a shortcut is rejected the app offers up to three alternatives inline.
They’re a fixed per-platform list rather than a check of what’s free on your
machine, so treat them as a starting point and not a guarantee.