In the US it's any electronic device, not just phones. CBP's own rules (Directive 3340-049A, from 2018) define it broadly: laptops, tablets, cameras, hard drives, game consoles, anything that stores data.

The directive splits searches into two kinds:

• Basic search: an officer manually looks through the device. No suspicion needed.
• Advanced search: they connect external equipment to copy or analyze the contents. That officially requires reasonable suspicion or a national security concern, plus supervisor approval.

One detail that's useful for planning: the directive says officers are only supposed to search what's stored on the device itself, not data that lives only in the cloud, and they're meant to ask you to disable network connectivity first. So something that just syncs from a server once you're home (and isn't cached locally) is in a different position from files on the disk. Courts in different circuits have also ruled differently on how much suspicion is needed, so it's not entirely settled.