Samsung Galaxy S24+ app keeps crashing, freezing or will not open

The checks in more detail

Restart it, and check Settings, Software update, because Samsung's monthly patches address crashes and a pending update can be the whole answer. Technobezz and TheDroidGuy both describe memory pressure from too many background apps as a common cause, so close apps from the recents screen and look at Device care, Memory. Safe mode is the best test for an app conflict. Hold the side key and Volume down until the power menu appears, then press and hold Power off until the Safe mode prompt shows and tap it. In Safe mode only the apps that shipped with the phone run.

If the crashes stop, a third-party app is responsible; restart normally and uninstall the most recent apps one by one until the crash stops. The S24+ has 12 GB of memory and a fast processor, so it should not run out of memory under normal use, which makes a leaking app the more likely cause. Also check that storage is not almost full, since a phone with under a gigabyte free behaves erratically, and that the date and time are set to automatic. If the problem began right after a One UI update and persists, back up and use Device care, or Smart Switch on a computer, to repair the software.

Persistent crashes in Safe mode need Samsung service. Keep a note of which apps fail and when, because the pattern tells you the cause: apps that crash only after the phone has been on for days suggest memory pressure and a restart each week helps, apps that crash only on Wi-Fi suggest a network problem and not the app, and apps that crash only right after you open them suggest a bad update. If a banking or work app crashes, tell its developer which One UI version you have, as they use that to reproduce the fault and release a fix.