What causes a PC to "come out of hiding"?

Question

By Hiding, I mean the PC has successfully gotten a Stealth check that beats an opponent's Perception / Passive Perception and is hidden from that opponent.

Other than attacking, which automatically breaks Hiding, and voluntarily coming out of hiding by yelling or, per the Hiding paragraph (under the Dexterity ability checks section) in the SRD/PHB, "knocking over a vase" and similar actions, are there any specific actions that will break Hiding?

The same paragraph noted above says:

In combat, most creatures stay alert for signs of danger all around, so if you come out of hiding and approach a creature, it usually sees you. However, under certain circumstances, the DM might allow you to stay hidden as you approach a creature that is distracted, allowing you to gain advantage on an attack roll before you are seen.

The part that says "if you come out of hiding" seems open to interpretation, but from what I can find in the rules only the voluntary breaking/dropping of Hiding, or attacking, will break the effect. I can't find anywhere where the rules say "leaving cover" will cause Hiding to break, nor can I find anything indicating that taking damage from an AOE would have any effect on the Hiding status of a target.

Are there any rules specific situations where Hiding is negated other than what is noted above?

I'd like to see if the sages here might have more insight into this.

Answer 1

"if you come out of hiding and approach a creature" refers to moving out in the open, where you can be seen clearly, as stated earlier in the rules:

You can’t hide from a creature that can see you clearly...

5e rules designer Jeremy Crawford has also confirmed this:

You can attack while hidden and gain the benefit. But if you run out into the open and then attack, you're not hidden when you attack.

However, as implied by the rules and his tweet, as long as you don't fully expose yourself, you can peek out from whatever you're hiding behind to make an attack.

Shooting from cover and running out into the open aren't the same thing.

It's also worth pointing out that hiding in combat imposes no limitations on your movement speed. This is a common point of confusion because of the Travel Pace rules.

Stealth imposes no movement reduction in combat.

In short, as long as you stay out of sight and don't do anything noisy, you'll remain hidden until an enemy moves into a position where you can be seen clearly, or uses the Search action and succeeds on an active Perception check to find you.

Jeremy talks about Stealth and Hiding at length in this episode of Dragon Talk. Besides touching upon some of these points, he also explains that the hiding rules are deliberately open-ended because there are too many circumstances that could influence whether you can get away with being sneaky. Rather than limit players to a set of rules that's too rigid or naive, or bogging down the game with excessively complex hiding rules, they left it up to the DM to make exceptions as needed and work with the players rather than against them.

---

With all that said, there is one action that's not explicitly called out in the rules but will most likely expose you: casting a spell with a V component. From the rules:

The words themselves aren’t the source of the spell’s power; rather, the particular combination of sounds, with specific pitch and resonance, sets the threads of magic in motion.

When asked how loud the V components need to be, Jeremy said this:

The verbal component of a spell must be audible to work. How loud is audible? That's up to the DM.

Although the level of loudness is left up to the DM, "audible" by definition means it can be heard.

Answer 2

This is probably down to DM interpretation; I'd rule that any action that has a chance to draw attention to the character will have a chance to break hiding.

For example, if a hidden character is approaching a monster (that failed its passive Perception check before) and the player acts out something that ends up as a quick move, this would have a chance of breaking hiding: the quick move may create air movement and the monster may get another passive Perception check.

Another example could be something reflexive in the room and the character moves into the line of sight of that - the monster now may have another passive Perception check because there's now extra detail in the environment that may give the character away. When the character was hiding behind the curtains (when the monster got the first passive Perception check) this wasn't an issue because the character wasn't visible in that reflexive surface.

None of these are attacks and they're not voluntary "breaking hiding" actions by the player but the end result is that the player may get noticed. A character action doesn't have to be very loud to draw attention, it just needs to alter the environment enough to warrant a look.