D&D 5E Investigation vs Perception

[robus]

Here's another easy rule of thumb:

• Perception takes a split second; it can be done for free or as a reaction, or maybe as long as your entire action if you're actively scanning around.
• If it takes longer than a single turn, it's Investigation, whether it be multiple rounds, minutes, hours, or even days.

Actually I think a different rule of thumb applies:

• Action is completed in a single turn? Active check.
• Action takes multiple turns? Passive check.