just to make sure; for confirmation
Used when double-checking or verifying something to avoid mistakes. Often placed at the beginning or end of a sentence.
Just to make sure, please check it one more time.
For confirmation, I sent the meeting time by email.
just in case; as a precaution
Used when taking preventive action against a possible future problem, even if unlikely. Similar to 念のため sense 1 but emphasizes risk avoidance rather than verification.
I'll take an umbrella just in case.
I bought spare batteries as a precaution.