When hiding, how close can you get to enemies before they can potentially detect you?

Question

The following situation: 2 Members of the party try to sneak up on distracted enemies. The other two, not stealth proficient players want to stay 20 feet behind, not roll stealth and join after the others. The approach is fine by me, but I am really confused about how near they can get before being noticed. This is important because I need to know how long they will take to join the fight afterward.

If I had to guess, I would say there is a detection range, how far a creature can detect others. Is there any rule for that or does the DM have to arbitrarily decide every time? Also, how does the alertness of the detecting creature and the environment (i.e. reverberation in a dungeon) factor into this?

Answer 1

There isn't a hard rule, so it's up to the DM and table

Without explicit information about detection range, this becomes a table dependent judgement that will rely on environment, creatures, etc. In general, I do the horrible thing and try to think of real world scenarios to help guide me.

Does being 20' back make sense for the scenario? Are there places to be out of sight and sound?

Or is this a situation where the enemies can pick out problems from farther away for reason X?

Being reasonable, assessing the specific situation, and communicating with your players what you think is reasonable and getting them to buy in is how you should proceed with this.

You can use ability checks to help guide you, or use certain triggers that make sense for that environment for an ability check.

As long as you are reasonable, consistent, and communicate your plans, then these issues work themselves out at the table.

Answer 2

Creatures are assumed to automatically notice other creatures that are within the range of their sight or hearing, unless they make Stealth checks

The DMG offers a limited amount of guidance about how to determine whether or not creatures detect each other. In the exploration section of chapter 8 ("Running the game"), it states:

Noticing Other Creatures

While exploring, characters might encounter other creatures. An important question in such a situation is who notices whom.

[...]

If neither side is being stealthy, creatures automatically notice each other once they are within sight or hearing range of one another. Otherwise, compare the Dexterity (Stealth) check results of the creatures in the group that is hiding with the passive Wisdom (Perception) scores of the other group, as explained in the Player’s Handbook.

Unless a creature actually attempts to be stealthy and makes a stealth check, it is assumed to be automatically noticed by any other creature once it gets within the range of their sight or hearing. Of course, this just raises the question of what the range of vision or hearing is.

Unfortunately this is entirely up to the DM's discretion for range of hearing, but for vision, this is quite clearly defined. The DMG in the same section also states:

When traveling outdoors, characters can see about 2 miles in any direction on a clear day, or until the point where trees, hills, or other obstructions block their view. Rain normally cuts maximum visibility down to 1 mile, and fog can cut it down to between 100 and 300 feet.

And we also have the PHB's rules about vision and light:

In a lightly obscured area, such as dim light, patchy fog, or moderate foliage, creatures have disadvantage on Wisdom (Perception) checks that rely on sight.

A heavily obscured area—such as darkness, opaque fog, or dense foliage—blocks vision entirely. A creature effectively suffers from the blinded condition when trying to see something in that area.

The presence or absence of light in an environment creates three categories of illumination: bright light, dim light, and darkness.

Bright light lets most creatures see normally. [...]

Dim light, also called shadows, creates a lightly obscured area. [...]

Darkness creates a heavily obscured area.

Here we see that a creature cannot see anything that is heavily obscured with respect to it, so will not automatically notice creatures that are in darkness until they are either close enough to hear or get within range of a light source or darkvision. It's also obvious that creatures who have full cover from one another cannot see each other, but can see each other if there is less than full cover involved.

Altogether, if two creatures are close enough to meaningfully interact, they are certainly close enough to see each other and will notice each other automatically, unless there are obstructions between them sufficient to grant full cover or some other impediment to visibility which makes one or the other heavily obscured. Without such circumstances, the creature must make a stealth check if it doesn't want to be noticed.

In the circumstances of your post - assuming that there were no special conditions of lighting or fog or other obstructions that would have made someone 20 feet further away actually impossible to see - the enemies should, by RAW, have noticed the unstealthy characters approaching as soon as they had line of sight, even if they are distracted.

Of course, it is important to note that these rules assume that stealth checks are opposed by a creature's passive perception, and if circumstances would grant them disadvantage on a perception check - for instance, if you judge they are distracted by something - that disadvantage translates to a -5 penalty to their passive perception score. So, even characters who aren't particularly skilled at stealth still have a good shot at sneaking up on distracted, unaware enemies.

Answer 3

It's entirely up to the DM to figure out when (and if) to roll

In the Basic Rules, regarding Ability Checks:

An ability check tests a character's or monster's innate talent and training in an effort to overcome a challenge. The DM calls for an ability check when a character or monster attempts an action (other than an attack) that has a chance of failure. When the outcome is uncertain, the dice determine the results.

The DM could factor in any number of things into when and where to make stealth rolls: Distance, spaces to hide in, how distracted are the enemies, ambient noise, party members that "think" they are whispering but are trying to hold long discussions...

And the check could happen any time in the enemy's perception range; but that varies also. The enemies might not see the characters approach, but they might be noisy so the perception range could be farther than their darkvision. Or the enemies could have tremorsense so they feel the approach even though there is plenty of cover.

There are no hard and fast rules as to "when".

Answer 4

There is no hard rule

The DM decides but it isn't arbitary. The DM should decide the DC based on the situation. A few examples are:

• Are the enemies on alert? If they're actively expecting trouble the DC is higher
• Is the party immediately identifiable as a threat? If you're spotted but the enemy is walking around town and passing a lot of people you the DC is lower than if spotting you breaks the surprise
• Lighting - if you're coming up on an enemy without dark vision and keep to the shadows the DC to pass is lower
• Perception level - if the enemy has a low perception score then the DC is lower
• Terrain - Some of this is down to player description. Are you crossing a big open field 20ft behind them? If they glance around then you're much more likely to be spotted -> higher DC
• How fast are you moving? If they're running (i.e. max speed, or dashing -double max) then the party are going to have to do the same to keep up. If thats the case then you'll have a harder time keeping quiet - higher DC

The list can go on but really it just depends on the DM and the party. The DM should know what your + to stealth is and that'll give them an idea of how high or low to set the DC relative to the reward you get for succeeding.

When you're planning you should consider the situation too - is your heavy plate fighter running 20ft behind going to have their clinking armour echo down the alley way? Thats something that might prick up the ears of your enemy.

Answer 5

There isn't a set distance that I'm aware of

I'm not familiar with any official guidance on this question, which seems sensible because the closest one creature can get to another without risking detection should be based on lots of factors besides distance alone. At its core, this requires the DM to integrate several pieces of information (which you have outlined in the question):

• How skilled are the observers at detecting motion/sound/scent, etc.?
• How skilled are the sneakers at avoiding detection?
• How does the environment make sneaking easier or more difficult?
• How does the situation make sneaking easier or more difficult?
• What does being detected mean versus being undetected?

A combination of these will determine what the "detection radius" might be for undefined sensory abilities. But D&D 5e has largely moved away from the highly reliable, precise rules of other editions and systems (perhaps most notably D&D 3.5e).

The first two items in my list are explicitly defined by skill ratings: creatures have Perception and Stealth scores, so you don't have to worry about determining those in the moment.

The third and fourth are generally expressed in D&D 5e with Advantage and Disadvantage: it's either easier than usual or more difficult than usual for sneaking/detection of sneaking.

The final item is totally context and DM dependent. If being detected means giving some signal that the observers will investigate, that suggests a different situation than detection meaning that an observer picks out a specific face in a large crowd of people.

Some defined sensory abilities do list a specific range, and those are inherently clear. If you're trying to tiptoe towards a creature with Tremorsense and enter the area in which that trait is relevant, your sneaking is unlikely to go well.

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Skill checks cover attempts, and technical rule wangling does not

A roll for a skill check covers your entire effort to be sneaky in a situation where failure is possible. Your character wouldn't know exactly how close they can approach a given person and remain undetected, and even if they did it's possible for them to make a mistake in some way.

If you want to remain undetected while approaching a potential observer, you would roll Stealth to see how successful you are in that effort regardless of other factors. That is usually contested by passive Perception or a Perception roll. In some cases it's a Stealth roll against a static difficulty rating. But characters (generally) don't get to skip ability checks by exploiting precision in mechanical rules.

The DM does need to integrate relevant information to define these checks, but 5e has a pretty streamlined way to do that: skill checks, Advantage/Disadvantage, and difficulty rating. That might play out narratively as the characters getting no closer than 20 feet (maybe they would have Disadvantage if they were closer, maybe the DC would be higher, maybe the observers would have Advantage, etc.), but players don't usually get to declare a successful result because they have plan X without rolls.

Answer 6

This is a situation where you'd use group checks.

Simply put, in a scenario where the group as a whole is sneaking, you'd want to use the rules for group checks, using the rules on p. 175 of the PHB.

To make a group ability check, everyone in the group makes the ability check. If at least half the group succeeds, the whole group succeeds. Otherwise, the group fails.

Basically, if there are two stealthy and two less-stealthy members of the group, they don't need to hand back to avoid their actions ruining the stealth of the group, though if they want to narrate their actions that way, that's fine. They all roll, and if at least half the group succeeds, everyone succeeds.

Answer 7

Welcome to stack exchange, I hope I can help you clear up the rules on stealth.

Let's look at the exact wording in the PHB (player's Handbook) on stealth (emphasis added by me):

Make a Dexterity (Stealth) check when you attempt to conceal yourself from enemies, slink past guards, slip away without being noticed, or sneak up on someone without being seen or heard.

The rules specifically allude to the idea of sneaking up on an opponent and in fact all the references to the use of stealth are based on the idea of stealth to move quietly is while quite close to an enemy.

Still, stealth can seem overly restrictive in 5th Edition if you overlook a very important "errata" (a kind of 'update' for the rules):

Hiding (p. 177). The following sentence has been added to the beginning of this section: “The DM decides when circumstances are appropriate for hiding.” The first sentence of the second paragraph now begins, “You can’t hide from a creature that can see you clearly …”

This is a significant change from the initial release which said "you can't hide from a creature that can see you." Period. This meant it was presumably impossible to peek around a corner to see if anyone is there as you can technically be seen at all when doing that.

So what does it take to not be seen clearly?

Further on the same page 177 of the PHB:

under certain circumstances, the Dungeon Master might allow you to stay hidden as you approach a creature that is distracted, allowing you to gain advantage on an attack before you are seen.

This is the rules basis for sneaking up on an opponent: distraction.

Not distance.

You have to decide what is enough of a distraction. It may be a distraction your players to create or or wait for their opponent to do something that would distract themselves.

As to the rest of the party who stays behind, if they aren't doing anything like "slinking past" or "slipping away" or "sneaking up" on an enemy then they shouldn't have to make stealth rolls. That doesn't mean they can do anything, if they are shouting conversations across the room that will give away their presence up to 100ft.