Light and dark
hiy has a light mode and a dark mode, and a toggle to switch between them. Whichever you pick applies everywhere on the site — the toggle itself isn't on every page, but the choice always is.
Where to find it
Signed out — on the homepage, pricing, docs, or any other marketing page — open Resources in the header and pick Light mode or Dark mode at the bottom of the menu. On a phone, tap the menu button and it's the last row in the panel. A page without that header, like someone's public twin page, still opens in whichever theme you last chose; it just doesn't offer a way to change it there.
Signed in, open your account menu (the avatar in the dashboard's rail, or the top bar on a phone) and choose Light mode or Dark mode. The label names what you'll switch to, not what you're on now, so it reads "Light mode" while you're still looking at the dark one.
Both are the same setting. Switch it from the header, and your dashboard opens in whichever one you left it in.
It's remembered on this device
Your choice is saved in the browser you made it in. Sign in on a different phone or laptop and hiy starts back on the default there, until you choose again on that device too.
hiy opens dark by default
The grainy dark wallpaper is what a first-time visitor sees — even if their phone or computer is set to light mode. hiy doesn't read that system setting for its own pages; the wallpaper is too much of the point to leave to it. Pick light mode once and it's remembered from then on, on that device.
Your embed doesn't follow it
If you've put your twin's chat on your own site (see Embedding), it ignores this setting entirely — yours and every visitor's. It looks instead at whoever's actually looking at it: their own device's light or dark setting, the same signal most embedded widgets already follow. That's deliberate. A choice you make on hiy.ai shouldn't quietly follow you onto someone else's page, and an embed that always matched your hiy.ai theme would do exactly that to every visitor who opens it.