Does approving a sign-in also trust that device?
Yes. Once approved, that browser is added to your trusted devices and will not be challenged again until you remove it — you can see and remove it from your security settings on either the website or the app.
From the guide Approving Sign-ins on Your Phone.
Where to find all of this
| Where | What you can do |
|---|---|
| Website — Settings → Security | See which of your phones can approve a sign-in and how each is locked, review and remove trusted devices, and manage codes and your authenticator app. |
| App — Settings → Sign-in & app lock | Set, change or remove your PIN or pattern, turn Face ID or your fingerprint on or off, and review or remove trusted devices. |
Read the whole guide: Approving Sign-ins on Your Phone