D&D 5E Determining Visibility [RAW]

Okay, this came up recently and I thought I knew the answer, but thought I would look it up to make sure I had it right (as written). I know previous editions had specific rules regarding center and corner etc, but, I couldn't find it in the PHB or DMG...

So, when playing on a map (5ft grid), when can creatures see each other? Is it from the center of the 'looking' creature to the center of the other creature? Any corner of the 'target' creature? Or any corner to any corner? And can someone point me to the source? Thanks!

(Note, I'm not talking cover, but that wouldn't be bad to add in either.)

DMG Page 251- Line of Sight from Chapter 8: Running the Game said:

To precisely determine whether there is line of sight between two spaces, pick a corner of one space and trace an imaginary line from that corner to any part of another space. If at least one such line doesn't pass through or touch an object or effect that blocks vision such as a stone wall, a thick curtain, or a dense cloud of fog- then there is line of sight.

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According to this, it seems like it's from any corner to any corner.

When not otherwise specified in 5e, you use common sense. It is from the eye (or other sensory apparatus) of the viewer to an actual visible part of the creature being viewed. There is business in the DMG about determining cover based on 5ft squares and corners, but these are optional and not terribly well written rules. For actual sight itself we default to common sense.

Unless the subject is a gelatinous cube they are not physically filling the entire space they occupy. They are somewhere inside of it. Seeing the very edge of someone's square should not make them visible, seeing the center or somewhere near it probably should unless it is a very unusual creature.

Cover is determined by drawing a line from any one corner of the attacking creature’s space (or the origin point of a spell) to each corner of the target square. If one or two of these lines is obstructed, a creature in that square has half cover from the attacker or the spell. If three of these lines are obstructed, it has three-quarters cover. If all four are obstructed, it has total cover.


Now, this doesn’t necessarily tell you whether or not the attacker can see the target. That is left up to the DM to determine. Certainly total cover blocks line of sight. Half cover probably doesn’t in most cases, but the DM might allow a creature with half cover to duck behind whatever is covering them to block line of sight, perhaps using the Hide action and/or making a Dexterity (Stealth) check. Three-quarters cover has the same ambiguity, though most DMs will probably be more willing to rule that a creature with three-quarters cover can block line of sight to itself than a creature with half cover.

The space a creature occupies is much like quantum particles, they are assumed to occupy all points of the square at any time. It's an abstraction because people are really moving around.

The official rule is in the DMG Chapter 8 Running the Game under the combat section.

Line of Sight​

Visibility can be an endless trap of overthinking. Following the rules like a computer would can result in some silly ramifications. My advice is to tell the players that at times you'll overrule the rules on visibility to make sure things make sense - and then to make sure you overrule them in favor of the PCs most of the time. To that end, I've:

• Allowed an archer to lean so far they fall over in order to shoot around a corner that was slightly blocked off by a wall.
• Allowed PCs to see the tendrils of a monster that was technically behind the wall, but had 20' reach and was lashing out at other PCs.
• Allowed a monster that was 15' into fog know the exact location of an enemy despite the fog blocking line of sight beyond 5'... because the PC in question was using a magical effect that gave off blinding light.

Stealth and visibility are two places where I focus more on making sure the story is good rather than that the details are 100% by the book.

Benjamin Olson said:

When not otherwise specified in 5e, you use common sense. It is from the eye (or other sensory apparatus) of the viewer to an actual visible part of the creature being viewed. There is business in the DMG about determining cover based on 5ft squares and corners, but these are optional and not terribly well written rules. For actual sight itself we default to common sense.

Unless the subject is a gelatinous cube they are not physically filling the entire space they occupy. They are somewhere inside of it. Seeing the very edge of someone's square should not make them visible, seeing the center or somewhere near it probably should unless it is a very unusual creature.

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By asking specifically for a RAW interpretation, the OP was certainly not looking for common sense. The RAW is all but common sense. It grants every combatant full 360 vision of almost unlimited range, perfect knowledge of where everyone is located in a fight, etc. None of it is realistic or common sense; as explained above by Oofta, it is an abstraction that we accept for the sake of gameplay (just like hp).

It would be more interesting to see specific examples and how different DMs would rule (if it even mattered) about whether or not a character can see another or not. And usually, it mostly matters for spellcasting purposes, and I think most DMs would allow the spell to be cast (same reason that lots of DMs don't bother with cover rules).

FarBeyondC said:

According to this, it seems like it's from any corner to any corner.

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Well, literally from any corner to any part.

Note also that other creatures, which normally grant some degree of cover, do not block vision, unless, of course, the cover is total, which is a matter to be determined by the DM.

Charlaquin said:

Cover is determined by drawing a line from any one corner of the attacking creature’s space (or the origin point of a spell) to each corner of the target square. If one or two of these lines is obstructed, a creature in that square has half cover from the attacker or the spell. If three of these lines are obstructed, it has three-quarters cover. If all four are obstructed, it has total cover.

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Now, this doesn’t necessarily tell you whether or not the attacker can see the target. That is left up to the DM to determine. Certainly total cover blocks line of sight. Half cover probably doesn’t in most cases, but the DM might allow a creature with half cover to duck behind whatever is covering them to block line of sight, perhaps using the Hide action and/or making a Dexterity (Stealth) check. Three-quarters cover has the same ambiguity, though most DMs will probably be more willing to rule that a creature with three-quarters cover can block line of sight to itself than a creature with half cover.

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DMG, p. 251 states that four blocked lines is also 3/4 cover. Only if it is somehow established that the attack cannot reach the target does it qualify as total cover. (Edit: This applies just as well to three blocked lines.)

I think whether a target can be seen is pretty well covered by the rules for determining line of sight on the same page.

jgsugden said:

Visibility can be an endless trap of overthinking. Following the rules like a computer would can result in some silly ramifications. My advice is to tell the players that at times you'll overrule the rules on visibility to make sure things make sense - and then to make sure you overrule them in favor of the PCs most of the time. To that end, I've:

• Allowed an archer to lean so far they fall over in order to shoot around a corner that was slightly blocked off by a wall.
• Allowed PCs to see the tendrils of a monster that was technically behind the wall, but had 20' reach and was lashing out at other PCs.
• Allowed a monster that was 15' into fog know the exact location of an enemy despite the fog blocking line of sight beyond 5'... because the PC in question was using a magical effect that gave off blinding light.

Stealth and visibility are two places where I focus more on making sure the story is good rather than that the details are 100% by the book.

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This, this, exactly this. The stealth and visibility rules are sadly not the best, so IMO it's much more important to make rulings which conserve realism and playability as much as possible than to focus purely on RAW. I say, speaking as a longtime rules lawyer.