I mean, my solution to 5.5e stealth is to use 5e rules -- yes, they're far more dependent on the DM's rulings about when circumstances are appropriate for stealth, but I'd rather have an explicit DM's call than incomprehensible rules.

While taking the Search action let you make a Wisdom (Perception) check, it's not a neccessity. You can make one without taking the Search action.

How often DM ask player characters for a Wisdom (Perception) check to notice something?

Sometimes, asking players to make Wisdom (Perception) checks for their characters tips them off that there's something they should be searching for, giving them a clue you'd rather they didn't have. In those circumstances, use characters' Passive Perception scores instead.

I've been mulling this over for a bit now, and the passage "Sometimes..." is just not sitting well with me. Let's start with the primary assumption of how the game is meant to be played: Players describe their character's actions (lower case, general, descriptive actions), and the DM narrates the outcomes, sometimes calling for checks.

If this assumption is incorrect, then you can tell me why and ignore the rest of this post.

However, if that's true, then I don't really understand how that "Sometimes..." passage ever comes into play. If they players are not describing that they are searching for something, then why would you, as a DM, call for an active check? If you don't, then you are already not tipping off your players that "there's something they should be searching for". However, if the players are already saying they are performing actions that would reasonably cause a DM to call for a Perception Roll, then you are already past the point where tipping them off would change their actions.

It seems that the passage assumes that the game is actually played differently to how they meant it to be played. That, without a players actually describing their character as searching for anything, a DM might call for a Perception Roll, and if they don't want to tip their hand, they can fall back on Passive Perception. But that puts Passive Perception not in a position of stopping information for being given to players, but of actually doing so—when PP is high enough to actually notice something. The way the "Sometimes..." passage is written is counter to itself. You use PP to give the players information without them rolling, not to deny them information by calling for a check the players never described actions requiring.

Quote from sabin76 >>

However, if that's true, then I don't really understand how that "Sometimes..." passage ever comes into play. If they players are not describing that they are searching for something, then why would you, as a DM, call for an active check?

Because it's a way to smooth out gameplay. If you're exploring a dungeon, having the players call out "I listen at the door" at every door, and "I search the room" every time they find a new room (or worse, search for traps every 10' in a corridor), rapidly gets tedious and annoying, so you assume they're taking an average level of caution all the time.

Quote from sabin76 >>

I've been mulling this over for a bit now, and the passage "Sometimes..." is just not sitting well with me. Let's start with the primary assumption of how the game is meant to be played: Players describe their character's actions (lower case, general, descriptive actions), and the DM narrates the outcomes, sometimes calling for checks.

If this assumption is incorrect, then you can tell me why and ignore the rest of this post.

However, if that's true, then I don't really understand how that "Sometimes..." passage ever comes into play. If they players are not describing that they are searching for something, then why would you, as a DM, call for an active check? If you don't, then you are already not tipping off your players that "there's something they should be searching for". However, if the players are already saying they are performing actions that would reasonably cause a DM to call for a Perception Roll, then you are already past the point where tipping them off would change their actions.

It seems that the passage assumes that the game is actually played differently to how they meant it to be played. That, without a players actually describing their character as searching for anything, a DM might call for a Perception Roll, and if they don't want to tip their hand, they can fall back on Passive Perception. But that puts Passive Perception not in a position of stopping information for being given to players, but of actually doing so—when PP is high enough to actually notice something. The way the "Sometimes..." passage is written is counter to itself. You use PP to give the players information without them rolling, not to deny them information by calling for a check the players never described actions requiring.

DUUUUDE! Thats what ive been saying!

If theyre searching, have them roll and use that.

If theyre not searching then their powers of observation should NOT be the average score they would get if theyre searching and ROLLED.

so passive should be lower.

Quote from SunIsGettingRealLow96589 >>

"Sometimes, asking players to make Wisdom (Perception) checks for their characters tips them off .... In those circumstances, use characters' Passive Perception scores instead."

Thats an optional rule dm's MAY employ. If dm wants to withhold information from players, the dm MAY use passive perception instead of revealing information by asking for a perception check.

The rule is optional. The dm may follow it if they wish. Nothing in the wording of the rule says passive perception MUST be an always on measure that the dm is required to use at all times.

No, "may" is not in the rules, but again, the rule being quoted is an optional rule.  

Although a few folks have made this argument in this thread, this is simply incorrect.  It's not even ambiguous.

This text is NOT describing a situation where this rule could be applied and "sometimes" the DM will apply the rule.

No.

This text follows a previous paragraph which basically says that when a creature hides, other creatures can always search for it.  Then it basically says, but "sometimes" other creatures won't know to search for anything.  In those circumstances, use characters' Passive Perception scores instead [every time, NOT sometimes].

That's written in the style of an instruction, not a suggestion.  It's clear and it's not ambiguous.

Quote from SunIsGettingRealLow96589 >>

Hiding/percieving a hiding enemy is not applicable to "avoiding tipping off the players". 

 

It absolutely is.

There are generally two scenarios that come up often in the game:

In one case, you are already in combat, you are aware of the combatants and one of them Hides.  In this case, the DM doesn't have to worry about tipping off players.  If they want to search, they can search.  They know that there is something that can be found.  In this case, they would have to search because Passive Perception has already failed when the creature successfully hid.

In the second case, you are out of combat, and you are not aware of any potential combatants.  They are setting up an ambush in advance.  In this case, the DM does not want to tip off the players.  When the hidden creatures are about to spring the ambush, the DM checks Passive Perception to see if they are surprised.  In this case, there is no reason for the players / characters to declare that they are searching for anything.  The only realistic way that they should be able to spot this ambush is via Passive Perception unless there is some special highly suspicious narrative going on or whatever.

Please keep in mind that I am well aware that most likely a vast majority of games are not actually run this way.  When I watch other people play online, even with highly "experienced" groups, it is amazing how often the DM will stroke his chin and then say, completely out of the blue, "Hmmmmm, ok player . . . make a Perception check please".  By the RAW, this should literally NEVER happen.  Yet, people play like this all the time, which is fine of course.  Dice rolling is fun after all.

Quote from SunIsGettingRealLow96589 >>

And none of the rules you are quoting clearly state that passive perception is something that the dm must always apply as a counter to an enemy in the area hiding or attemtpting to hide.

 

Sure, they do.  The hide action provides a mechanism for finding a hidden creature with a Wisdom (Perception) check -- Passive Perception IS one such check.  Furthermore, the rules state that sometimes a creature won't actively search.  "In those circumstances, use characters' Passive Perception scores instead."  Why Passive Perception?  Because "Passive Perception is a score that reflects a creature’s general awareness of its surroundings. The DM uses this score when determining whether a creature notices something without consciously making a Wisdom (Perception) check".

Quote from SunIsGettingRealLow96589 >>

So copying and pasting the rules again, probably isnt going to change anything. 

I mean, honestly if people quoting the rules verbatim from the text bothers you for some reason, then you might be in the wrong place.  This is the Rules and Mechanics forum and quoting the rules is the main way to let other folks know what the rules actually say.  

Quote from SunIsGettingRealLow96589 >>

But you are absolutely, positively, without a doubt certain that your interpration is correct, and the only possible way that you can imagine that someone would disagree with your "overwhelming evidence" is if they dont understand your logic.

Yes, in this particular case that is true.  In general, I will say that the rules do suffer from ambiguity in many places.  This just isn't one of them.  Ambiguity really isn't the problem when it comes to the Hide mechanics.  The main problem, both in the 2014 and 2024 versions, is that the mechanic is spread out across more than a half dozen different places and across multiple books.  It's a bit of a project for the reader to really get the full picture from the text.  The information is all there, but it's not easily digestible.  

Quote from Natrel >>

At my table, you have to both succeed the 15DC check and beat their passive perception. If you beat the 15, congrats, you've done a proper job at concealing yourself. Your foot doesn't show up from behind that wall, you don't make a visible bump behind that curtain, you've properly wrapped your entire body inside your Nature's Mantle. But if you don't beat their passive perception, they notice subtle movements that you make, their hear your leather armor squeaking, they notice subtle reflections of light onto your Mantle... and they find you. That's what makes sense to me.

Bingo.

Quote from sabin76 >>

If they players are not describing that they are searching for something, then why would you, as a DM, call for an active check? If you don't, then you are already not tipping off your players that "there's something they should be searching for". However, if the players are already saying they are performing actions that would reasonably cause a DM to call for a Perception Roll, then you are already past the point where tipping them off would change their actions.

Yes!  I agree with this.  Why indeed would you call for an active check when nothing active is happening?

Quote from sabin76 >>

It seems that the passage assumes that the game is actually played differently to how they meant it to be played. That, without a players actually describing their character as searching for anything, a DM might call for a Perception Roll, and if they don't want to tip their hand, they can fall back on Passive Perception. But that puts Passive Perception not in a position of stopping information for being given to players, but of actually doing so—when PP is high enough to actually notice something. The way the "Sometimes..." passage is written is counter to itself. You use PP to give the players information without them rolling, not to deny them information by calling for a check the players never described actions requiring.

No, that's not what that text is saying.  The first paragraph is saying that a creature can always be found with the Perception skill -- finding a hidden creature is never an auto-success or an auto-fail.  This first paragraph is also written from a point of view that it's known that a creature took the Hide action.  In such cases, an obvious response might be to search for it.  But "sometimes" there might be a situation where there is no way to know to search for a hidden creature and in general the DM should not tip off the players in those cases.  That's when Passive Perception is used.  Really, a DM should never call for an active roll when the players have not declared that they are searching for something.  Doing so would tip off the players and doing so also just doesn't make sense.  Active rolls adjudicate actions.  It's not that the DM "can fall back on" using Passive Perception if they don't want to tip something off.  Instead, sometimes there might be something that can be found but the characters are not searching.  In which case we don't want to tip them off.  In those circumstances, use characters’ Passive Perception scores instead.

In addition, Passive Perception is NOT about providing information.  It's about achieving exactly the same result that an active Perception check would achieve.  The active and passive versions are BOTH Wisdom (Perception) checks.  The consequence of a success is the same in both cases, and the consequence of a failure is the same in both cases.  It's NOT a two-step process.  You do NOT say something like "Ok, because you have a high Passive Perception, you notice that there's something over there.  Now, roll a Perception check."  Again, I'm aware that a great many tables do play that way, but that's not what is intended.  Instead, Passive Perception is used to attempt to actually notice (find) the thing in the same manner that a successful active check might actually notice (find) the thing.

For example, you are walking down the road, and the goblins have previously set up an ambush.  The DM does NOT tip off the players by asking for a Perception check.  Instead, the DM uses Passive Perception.  If that fails, then the players and the characters STILL have NOT been tipped off.  The result is that combat starts and the characters are surprised.  On the other hand, if Passive Perception succeeds, then the goblins are found right then and there and combat starts without surprise.

Instead, sometimes there might be something that can be found but the characters are not searching.  In which case we don't want to tip them off.  In those circumstances, use characters’ Passive Perception scores instead.

You (mostly) had me until here. This uses the same language, and therefore the same logic as the passage itself. The problem is that this is all "behind the screen" as it were. You use PP to not tip the players off that there's something to search for, and yet, the only thing you do as a DM with that is give the players information if their PP is high enough. If not, you don't say anything, which is the same as not using their PP in the first place. If played "correctly" you never actually "tip off" your players whether you use PP or not. In what way of playing the game by the rules would a DM ever "tip off" their players? Again, it just feels like that whole passage assumes that people don't play the way the game is written. In other words, the way you are describing the use of PP doesn't actually have anything to do with the rules' "rationale" for using PP.

Because it's a way to smooth out gameplay. If you're exploring a dungeon, having the players call out "I listen at the door" at every door, and "I search the room" every time they find a new room (or worse, search for traps every 10' in a corridor), rapidly gets tedious and annoying, so you assume they're taking an average level of caution all the time.

I actually think I might use "subtle rolls" for something like this. As a DM I can shut down the endless "I search!" loop pretty easily. What's harder is players metagaming when the first person who rolls gets a low number and everyone sees it. I watched a video recently that talked about "subtle rolls" where the players rolls, but never sees the result of their roll. I do, as the DM, and narrate the result, but the players are none-the-wiser about what number actually showed up. In essence, they roll behind my screen whenever their characters would have no way of knowing whether they "failed" a roll or not.

DUUUUDE! Thats what ive been saying!

 

If theyre searching, have them roll and use that.

If theyre not searching then their powers of observation should NOT be the average score they would get if theyre searching and ROLLED.

so passive should be lower.

I didn't quite come to the conclusion you did at the end, though you certainly have given me something to think about in that regard. All I was saying is that that particular passage seems to be logically self-defeating (mechanically, it can be made to work). The "reason" for Passive Perception doesn't line up with how it seems to be used as written.

Quote from sabin76 >>

I've been mulling this over for a bit now, and the passage "Sometimes..." is just not sitting well with me. Let's start with the primary assumption of how the game is meant to be played: Players describe their character's actions (lower case, general, descriptive actions), and the DM narrates the outcomes, sometimes calling for checks.

If this assumption is incorrect, then you can tell me why and ignore the rest of this post.

However, if that's true, then I don't really understand how that "Sometimes..." passage ever comes into play. If they players are not describing that they are searching for something, then why would you, as a DM, call for an active check? If you don't, then you are already not tipping off your players that "there's something they should be searching for". However, if the players are already saying they are performing actions that would reasonably cause a DM to call for a Perception Roll, then you are already past the point where tipping them off would change their actions.

It seems that the passage assumes that the game is actually played differently to how they meant it to be played. That, without a players actually describing their character as searching for anything, a DM might call for a Perception Roll, and if they don't want to tip their hand, they can fall back on Passive Perception. But that puts Passive Perception not in a position of stopping information for being given to players, but of actually doing so—when PP is high enough to actually notice something. The way the "Sometimes..." passage is written is counter to itself. You use PP to give the players information without them rolling, not to deny them information by calling for a check the players never described actions requiring.

Most ability check are the result of actions initiated by player characters, but often a DM can ask for a Wisdom (Perception) check to determine if you notice something, 

Or a Wisdom (Insight) check to determine if you dicern someone is lying.

Even a Wisdom (Survival) check to determine if you find a trail.

Regardless of the check involved, the DM could opt for a Passive Check instead if they don't want to tips them off that there's something they should be searching for.

Passive Perception is a score DM can use  instead of making a Wisdom (Perception) check, this wether you take the Search action or not.

If to make such a check you needed to take an action it would completely defeat the purpose. 

It reminds me when playing AD&D 2nd Edition when DM would call for an Observation check, if anyone remember the Proficiency ? 😀 

https://www.dndbeyond.com/sources/dnd/dmg-2024/running-the-game#Perception

"When to Call for a Check
An important time to call for a Wisdom (Perception) check is when another creature is using the Stealth skill to hide. Noticing a hidden creature is never trivially easy or automatically impossible, so characters can always try Wisdom (Perception) checks to do so."

So, npc is hidden. Player characters are entering hallway where npc is hidden. PLAYERS can initiate a wisdom/perception  check.  

Next paragraph says 

"Using Passive Perception. Sometimes, asking players to make Wisdom (Perception) checks for their characters tips them off"

This is the DM about to ask players to make a perception check? For reasons very unclear.  And then dmg says, instead of asking them, you could use passive perception instead.

The previous section says a PLAYER can initiate a check. 

The "sometimes" paragraph is tied to the -DM- asking for a check, but that should never happen. 

If the players DO ask for an active check, have them roll. 

If players do NOT ask for an active check, why would dm ask them to roll an active check? It shouldnt happen.

Quote from SunIsGettingRealLow96589 >>

https://www.dndbeyond.com/sources/dnd/dmg-2024/running-the-game#Perception

"When to Call for a Check
An important time to call for a Wisdom (Perception) check is when another creature is using the Stealth skill to hide. Noticing a hidden creature is never trivially easy or automatically impossible, so characters can always try Wisdom (Perception) checks to do so."

So, npc is hidden. Player characters are entering hallway where npc is hidden. PLAYERS can initiate a wisdom/perception  check.  

Next paragraph says 

"Using Passive Perception. Sometimes, asking players to make Wisdom (Perception) checks for their characters tips them off"

This is the DM about to ask players to make a perception check? For reasons very unclear.  And then dmg says, instead of asking them, you could use passive perception instead.

The previous section says a PLAYER can initiate a check. 

The "sometimes" paragraph is tied to the -DM- asking for a check, but that should never happen. 

If the players DO ask for an active check, have them roll. 

If players do NOT ask for an active check, why would dm ask them to roll an active check? It shouldnt happen. 

Just as a point of order, while I think the section you quoted about "When to call for a check" could be read as that a player initiates the check, the text doesn't explicitly say that.

This is from the DMG, and so directed at DMs. The section is about when you, the DM, should call for a check.

It says, "An important time to call for a Wisdom (Perception) check..."

This is discussing when the DM should call for a check from the players.

The next portion, "so characters can always try Wisdom (Perception) checks to do so..." doesn't actually imply the players are initiating anything. For one, it is talking about characters, and it just says "they can try." If I were your track coach, and I told the squad "today we are trying for 4 minute miles!" then the athletes are not initiating the attempt at a 4-minute mile. I am, as the coach, telling them to. But they are still going to try to do the 4-minute mile. Saying that the character can try a check to do something doesn't necessarily imply that it is the player initiating that check.

When to Call For a Check is addressed to DMs and is preceded by this:

Perception

As the DM, you're the interface between your players and the world of the game. You tell them what their characters perceive, so it's important to make sure you're telling them important information about their surroundings. The Perception skill and Wisdom checks made using it are key tools for you. This section offers guidance to help you use the Perception rules in the Player's Handbook.

Also players shouldn't just roll ability checks without context unless the DM ask for it.

Resolving Outcomes

You decide when a player makes a D20 Test based on what the character is trying to do. Players shouldn't just roll ability checks without context; they should tell you what their characters are trying to achieve, and make ability checks only if you ask them to.

Quote from MaximusArael020 >>.

The next portion, "so characters can always try Wisdom (Perception) checks to do so..." doesn't actually imply the players are initiating anything. 

If a rule says "characters can do something" really means the "dm can do something", then there is no point in trying to understand the rules at all. 

Quote from SunIsGettingRealLow96589 >>

Quote from MaximusArael020 >>.

The next portion, "so characters can always try Wisdom (Perception) checks to do so..." doesn't actually imply the players are initiating anything. 

 

If a rule says "characters can do something" really means the "dm can do something", then there is no point in trying to understand the rules at all. 

 This seems hyperbolic. I'm merely pointing out that because the text states a character can try something, that does not mean that the roll/action/reaction/saving throw/etc MUST have been initiated by the player, and instead could have been initiated by the DM calling for a check/roll/saving throw/etc. 

A character CAN attempt to avoid damage or effects from a spell by rolling a Saving Throw. That does not mean the player initiated that action.

Quote from sabin76 >>

Instead, sometimes there might be something that can be found but the characters are not searching.  In which case we don't want to tip them off.  In those circumstances, use characters’ Passive Perception scores instead.

You (mostly) had me until here. This uses the same language, and therefore the same logic as the passage itself. The problem is that this is all "behind the screen" as it were. You use PP to not tip the players off that there's something to search for, and yet, the only thing you do as a DM with that is give the players information if their PP is high enough. If not, you don't say anything, which is the same as not using their PP in the first place. If played "correctly" you never actually "tip off" your players whether you use PP or not. In what way of playing the game by the rules would a DM ever "tip off" their players? Again, it just feels like that whole passage assumes that people don't play the way the game is written. In other words, the way you are describing the use of PP doesn't actually have anything to do with the rules' "rationale" for using PP.

In my opinion, a lot of people are misinterpreting the "rationale".  The rationale is not "to avoid tipping off the players".  The rationale is that sometimes the players are not searching and they wouldn't have any reason to do so based on the information that they have and in all such cases you do not want to tip off the players.  Essentially, the text is saying . . . don't ask for a die roll here because then the players will know that they should be searching.  

Next, you've mentioned this bit a couple of times now that "the only thing you do as a DM with that is give the players information".  Can you clarify what you mean by that and where you are getting that from?  My suspicion is that this is wrong, but I guess it depends on what you mean and I might be misinterpreting what you are saying.

A Passive Perception check doesn't really give players "information".  It yields exactly the same result as an active Perception check.  For example, suppose there is a hidden creature with a DC 15 to be found.  In the first scenario your Passive Perception score is 16.  Result -- you find the hidden creature.  In the second scenario your Passive Perception score is 13.  But, for whatever reason you've chosen to actively search for this hidden creature.  You roll a 16.  Result -- you find the hidden creature.  It's exactly the same thing.

Quote from Plaguescarred >>

If to make such a check you needed to take an action it would completely defeat the purpose. 

The 2024 rules have pretty well clarified that this is indeed how the game is designed.  Active checks adjudicate actions.  The authors went through the trouble of formalizing some of the actions that previously weren't as well defined in 2014, such as the Magic action, the Influence action, the Search action, the Study action and the Utilize action.  In cases where we need to determine an outcome when no action was taken, we use the passive check mechanic:

PASSIVE CHECKS

Ability checks normally represent a character's active effort to accomplish something, but occasionally you need a passive measure of how good a character is at doing a thing. Passive Perception is the most common example. (See “Perception” later in this chapter.) You can extend the concept of a passive ability check to other abilities and skills. For example, if your game features a lot of social interaction, you can record each character's Passive Insight score . . .

Almost all of the skills in the game now align with one of the standard actions.  The three exceptions are all physical ability skills -- Acrobatics, Athletics and Sleight of Hand.  It should be reasonable to assume that those skills would apply to some sort of improvised action as determined by the DM.

Quote from SunIsGettingRealLow96589 >>

https://www.dndbeyond.com/sources/dnd/dmg-2024/running-the-game#Perception

"When to Call for a Check
An important time to call for a Wisdom (Perception) check is when another creature is using the Stealth skill to hide. Noticing a hidden creature is never trivially easy or automatically impossible, so characters can always try Wisdom (Perception) checks to do so."

So, npc is hidden. Player characters are entering hallway where npc is hidden. PLAYERS can initiate a wisdom/perception  check.  

As mentioned earlier, this particular paragraph is actually poorly written and should be tweaked via errata.  Characters never really "try" Perception checks, nor do the players "initiate" them.  Whether or not a check is made is always refereed by the DM.  The player can have the character search, in which case the DM should ask for a check.  Or the player can (knowingly or unknowingly) put their character into a situation where their Passive Perception would apply, in which case the DM should use the Passive Perception mechanic.  That first paragraph is establishing these options -- the hidden creature is never auto-found or permanently hidden.  They can always be found with good enough Perception.

Quote from SunIsGettingRealLow96589 >>

"Using Passive Perception. Sometimes, asking players to make Wisdom (Perception) checks for their characters tips them off"

This is the DM about to ask players to make a perception check? For reasons very unclear.  And then dmg says, instead of asking them, you could use passive perception instead.

Not quite.  It's not "you could use".  It's "In those circumstances, use characters’ Passive Perception scores instead."

Quote from SunIsGettingRealLow96589 >>

The "sometimes" paragraph is tied to the -DM- asking for a check, but that should never happen. 

If the players DO ask for an active check, have them roll. 

If players do NOT ask for an active check, why would dm ask them to roll an active check? It shouldnt happen.

YES!!!  I agree with this.  

__________

Again, we can all acknowledge that most tables are not currently being run this way.  It's very common for a DM to say, out of the blue, "make a Perception check".  But the mechanics given by the RAW result in running the game differently than that.  The authors of the rules could have done a better job of putting all of the necessary information for running these mechanics all together in one place.  

As a rule of thumb, active rolls are for actions.  There are some consequences to this which deviate from how people often play.  For example, consider this situation:

While proceeding down the corridor, all of a sudden, a group of 4 people dressed like knights approach from around the corner ahead of you and immediately attack.  They all have (some specific description) emblazoned on the breastplate and are all wearing (some specific description) style of helmet.  Roll for initiative.  Fighter, you're up.

Now, the fighter might ask something like "Do I recognize these symbols?  Can I tell which nation these people are from or to whom they are allegiant?"  And very often, the DM will respond with something like "Make a history check".  Now, the 2024 rules make it pretty clear that doing something like this will cost you your action unless we decide to extend the concept of Passive Checks pretty far to the point where we are now making Passive History checks by using the Passive Checks mechanic.  But mostly, people don't play that way.  Instead, the player rolls the die "for free" to gain this information on the fly.  But it's useful to know that that's just not the RAW way to run the game.  Once that is known and understood then we can deviate in well thought out ways if desired by the group.  But more often what happens is that people are just running the game outside of the RAW without actually realizing it.

Quote from up2ng >>

Again, we can all acknowledge that most tables are not currently being run this way.  It's very common for a DM to say, out of the blue, "make a Perception check".  But the mechanics given by the RAW result in running the game differently than that.

I would argue that if the rules don't match up with the way people are inclined to play, the rules should be changed.

Passive Perception and Search are not the same thing. Passive Perception is to notice something in plain sight while Search involves actively trying to find something. Indeed, a good rule of thumb is that if it's possible to notice it with Passive Perception, the roll for a Search is essentially automatic.

You might walk into a library and check Passive Perception to see if the players notice one of the books is slightly askew. However, it would take Search roll to discover that the book actually controls a secret door. If they didn't meet the Passive Perception about the askew book, they'd more or less automatically succeed on the Search roll to discover the askew book because the mere fact that you can detect it with Passive Perception means it's blindingly obvious to anyone who looks.

Nor is this some new thing with 2024 rules. It's how Passive Perception has worked for decades, across multiple game versions. The entire point of Passive Perception was to prevent the "We move 10' forward, check for traps" pattern. It was never intended - and never written in any version of the rules - to replace actual Search checks.

Quote from up2ng >>

Quote from Plaguescarred >>

If to make such a check you needed to take an action it would completely defeat the purpose. 

 

The 2024 rules have pretty well clarified that this is indeed how the game is designed.  Active checks adjudicate actions.  The authors went through the trouble of formalizing some of the actions that previously weren't as well defined in 2014, such as the Magic action, the Influence action, the Search action, the Study action and the Utilize action.  In cases where we need to determine an outcome when no action was taken, we use the passive check mechanic:

PASSIVE CHECKS

Ability checks normally represent a character's active effort to accomplish something, but occasionally you need a passive measure of how good a character is at doing a thing. Passive Perception is the most common example. (See “Perception” later in this chapter.) You can extend the concept of a passive ability check to other abilities and skills. For example, if your game features a lot of social interaction, you can record each character's Passive Insight score . . .

 

Almost all of the skills in the game now align with one of the standard actions.  The three exceptions are all physical ability skills -- Acrobatics, Athletics and Sleight of Hand.  It should be reasonable to assume that those skills would apply to some sort of improvised action as determined by the DM.

 You never seen DM ask for a Intelligence (Arcana, History, Investigation, Nature, or Religion) check without taking the Study action ? 

You never seen DM ask for a a Wisdom (Insight, Medicine, Perception, or Survival) check without taking the Search action ?

Quote from VerilyRaze >>

Nor is this some new thing with 2024 rules. It's how Passive Perception has worked for decades, across multiple game versions. The entire point of Passive Perception was to prevent the "We move 10' forward, check for traps" pattern. It was never intended - and never written in any version of the rules - to replace actual Search checks.

Prior to 5e, making a perception check was not an action (nor was hiding).