If a net is 10×10, can it hit four medium creatures, by RAW?

Question

This whole question assumes that the canonical Net weapon used for immobilizing a Large creature, is 10ft across; if your answer is based on a presumption that a net weapon isn't 10ft across, please cite evidence to support such a ruling (RAW strongly preferred).

TLDR: All the info about the size of a net, indicates 10×10, & attacks can target a location & then hit ¿(unseen)? creature(s) in that location, so it seems one could target a 10×10 area with a net... correct?

Due to disadvantage on ranged (thrown) attacks within 5ft & the net's range of 5ft, it seems the net has become notorious as a sub-optimal choice of weapon, but if there's any possibly of hitting any-&-all creatures inside a 10×10 area, that seems like a significant note for analyzing optimal usage.

The rules for Making an Attack (PHB p193), ostensibly allow you to target a creature, object, or location:
(emphasis mine)

Whether you're striking with a melee weapon, firing a weapon at range, or making an attack roll as part of a spell, an attack has a simple structure.

1. Choose a target. Pick a target within your attack's range: a creature, an object, or a location.

2. Determine modifiers. The DM determines whether the target has cover and whether you have advantage or disadvantage against the target. In addition, spells, special abilities, and other effects can apply penalties or bonuses to your attack roll.

3. Resolve the attack. You make the attack roll. On a hit, you roll damage, unless the particular attack has rules that specify otherwise. Some attacks cause special effects in addition to or instead of damage.

If there's ever any question whether something you're doing counts as an attack, the rule is simple: if you're making an attack roll, you're making an attack.

The item (weapon) listing for a net (PHB p149 & OpenSRD), has a special property in place of damage on a hit:

A Large or smaller creature hit by a net is restrained until it is freed. A net has no effect on creatures that are formless, or creatures that are Huge or larger.

A creature can use its action to make a DC 10 Strength check, freeing itself or another creature within its reach on a success. Dealing 5 slashing damage to the net (AC 10) also frees the creature without harming it, ending the effect and destroying the net.

When you use an action, bonus action, or reaction to attack with a net, you can make only one attack regardless of the number of attacks you can normally make.

Large creatures occupy a 10×10 space, & the net traps all assume a 10ft net, & personally it looks pretty silly to me when I picture a Large creature getting restrained by a 5ft net (perhaps by a bolo).

The DMG & XGE listings for a Falling Net & a Net Trap, both affect a 10x10 area:

Falling Net (DMG p122 & SRD)
Mechanical trap
This trap uses a trip wire to release a net suspended from the ceiling.
The trip wire is 3 inches off the ground and stretches between two columns or trees. The net is hidden by cobwebs or foliage. The DC to spot the trip wire and net is 10. A successful DC 15 Dexterity check using thieves' tools breaks the trip wire harmlessly. A character without thieves' tools can attempt this check with disadvantage using any edged weapon or edged tool. On a failed check, the trap triggers.

When the trap is triggered, the net is released, covering a 10-foot-square area. Those in the area are trapped under the net and restrained, and those that fail a DC 10 Strength saving throw are also knocked prone.

A creature can use its action to make a DC 10 Strength check, freeing itself or another creature within its reach on a success. The net has AC 10 and 20 hit points. Dealing 5 slashing damage to the net (AC 10) destroys a 5-foot-square section of it, freeing any creature trapped in that section.

Net Trap (XGE p113)
Simple trap (level 1–4, dangerous threat)
Goblins, with their propensity to enslave their enemies, prefer traps that leave intruders intact so the victims can be put to work in the mines or elsewhere.

Trigger. A trip wire strung across a hallway is rigged to a large net. If the trip wire is broken, the net falls on intruders. An iron bell is also rigged to the trip wire. It rings when the trap activates, alerting nearby guards.

Effect. A net covering a 10-foot-by-10-foot area centered on the trip wire falls to the floor as a bell rings. Any creature fully within this area must succeed on a DC 15 Dexterity saving throw or be restrained. A creature can use its action to make a DC 10 Strength check to try to free itself or another creature in the net. Dealing 5 slashing damage to the net (AC 10, 20hp) also frees a creature without harming the creature.

Countermeasures. A successful DC 15 Wisdom (Perception) check reveals the trip wire and the net. A successful DC 15 Dexterity check using thieves' tools disables the trip wire without causing the net to drop or the bell to ring; failing the check causes the trap to activate.

Again, absent any actual text to such effect, it seems silly to me to presume a mere 5ft net: When have we even seen such a small net depicted or used in actual combat? Particularly for a Large creature controlling a 10×10 space, a 10×10 net seems both a reasonable presumption & the most supported by the texts provided.

A net attack targeting a single creature is widely considered grossly sub-optimal, & a real net's minimum necessary area to reduce a Large creature's speed to zero, is pretty close to 8 or 10ft if we're being even a little bit realistic. A net weapon less than 10ft across for stopping Large creatures, both lacks believability & lacks support within the canonical texts that mention nets & their uses. Is there any 5e attestation for nets being smaller than 10ft?

Thus, it seems well supported that as a weapon, a typical net is 10ft×10ft, to cover the area controlled by a Large creature.

As seen in point 1 of the PHB rules for making an attack, the rules expressly allow an attack roll to target a location; which has (almost!) no utility except AoE. (As @Jason_c_o points out, the OpenSRD section on Unseen Attackers and Combat, states that "guessing the target’s location" automatically misses a creature if it "isn’t in the location you targeted", heavily implying if not outright stating that an unseen creature can be hit when its location is targeted. Judging by this part of the rules, attacks targeting the presumed location of an unseen creature, could affect any creature(s) in that location.)

Of the five Spell Attacks that can target a location instead of specifically targeting only a creature or objects, none would have any effect unless creatures or objects in that location could be affected. Noteworthy?

Upon review, Bombs, grenades, Dynamite sticks, & other thrown AoE items that allow targeting a location, all use an Action, not an Attack roll.

Even weapon attacks with 10ft Reach, usually can't hit multiple creatures with one attack; the only thing supporting this idea of a thrown net hitting 4 creatures, is the premise of targeting a location 10ft across by throwing an item that's 10ft across, at that space, & the fact that I haven't found any attack of any kind that targets a location, except for the possibility of targeting the space an unseen creature is (believed to be) in. I understand that this is a thin line of reasoning, which is why I'm looking for any & all RAW relating to what can or cannot be hit by an attack that is targeting a location.
(Big thanks to @Jason_c_o, for providing citation that directly relates to Attacks that target locations.)

So, in the case of a thrown net 10ft across, an attack roll targeting a location, using a net 10ft square, could hit up to 4 unseen medium creatures. Is this true?

If not, why? What rule prevents an attack roll with an item that has a large area, from targeting an area its own size?

If so, should the GM count the wielder's attack roll against the AC of each creature within the 10ft area, with any creature hit becoming grappled by the net? Basically just like any other AoE attack roll?

Of course, "dealing 5 slashing damage to the net (AC 10) also frees the creature without harming it, ending the effect and destroying the net", so as soon as one creature cuts its way out, they're all freed; but I'm uncertain as to whether I've interpreted this mode of attack correctly in the first place: Is an AoE really allowed by RAW?

(In fact, even the +3 Net, still has AC 10 & gets destroyed by 5 slashing damage; extremely limited use for a Very Rare magic item!)

Essentially, this question is asking whether targeting a location with an item 10ft across, has a chance (AC) to hit those creatures. If a 10ft object is thrown at a space, do all creatures in that space have a chance to get hit?

Can the wielder of a net that is ten feet across, target a location, with an attack using that 10ft×10ft item, to hit 4 ¿(unseen)? medium creatures with one attack?

Answer 1

All attacks have a single target unless otherwise noted

The first step in making an attack is:

1. Choose a target. Pick a target within your attack's range: a creature, an object, or a location.

The general rule is that every attack has a single target. There are a few specific cases that override this general rule, but the net is not one of them. Nothing in the net's description says it can target multiple creatures or target all creatures in an area, so that means a single net attack can only hit a single target.

(Note: If you want an example of an attack that does override this rule, see the Hunter ranger's Multiattack. This is a well-known exception that has generated its own fair share of questions on this site.)

You can't target multiple creatures by targeting a location

Generally, when you designate a target, you can only roll an attack against that target. So if you want to target a creature with an attack, you must actually target the creature with the attack. However, there are a few exceptions to this. One reason you might target a location instead of a creature is that you are trying to attack a hidden creature, as described in the section on unseen attackers and targets:

When you attack a target that you can't see, you have disadvantage on the attack roll. This is true whether you're guessing the target's location or you're targeting a creature you can hear but not see. If the target isn't in the location you targeted, you automatically miss, but the DM typically just says that the attack missed, not whether you guessed the target's location correctly.)

This rule is a special case that overrides the general rule above: you target a location, and if a creature is in that location, you get to attack that creature instead of the location. However, this still does not allow you to target multiple creatures with a single attack. As far as I know, there is no rule that allows an attack targeting a single location to attack multiple creatures.

The optional cover rules might give you 2 chances to hit

The optional rule for hitting cover allows an attack that misses a target behind cover to hit the object or creature providing cover for the original target:

First, determine whether the attack roll would have hit the protected target without the cover. If the attack roll falls within a range low enough to miss the target but high enough to strike the target if there had been no cover, the object used for cover is struck. If a creature is providing cover for the missed creature and the attack roll exceeds the AC of the covering creature, the covering creature is hit.

If you happen to be lined up with 2 potential target creatures, such that the closer one is providing cover for the further one, then targeting the further creature allows you to roll a single attack and potentially hit either creature. However, once again, the attack can only hit a single target: it either hits the original target or the covering creature, but not both.

The physical size of a weapon is irrelevant

A thrown net may very well be 10×10 or even larger when fully extended. However, using a large weapon does not allow you to target multiple creatures with one attack. Even a huge stone giant wielding an oversized greatclub or hurling a boulder attacks a single target at a time:

Greatclub. Melee Weapon Attack: +9 to hit, reach 15 ft., one target. Hit: 19 (3d8 + 6) bludgeoning damage.

Rock. Ranged Weapon Attack: +9 to hit, range 60/240 ft., one target. Hit: 28 (4d10 + 6) bludgeoning damage. If the target is a creature, it must succeed on a DC 17 Strength saving throw or be knocked prone.

There are no mechanics that give attacks with larger weapons an area of effect. Attacks that target an area similar to a spell are either rare or nonexistent in published materials; I certainly haven't seen any. Effects that target all creatures in an area nearly always do so by requiring those creatures to make saving throws, even if those effects have "attack" in their name (for example, an adult dragon's Wing Attack). The net's description does not specify an area of effect or a saving throw, and there are no mechanics for "implied area of effect".

(Note: the closest thing to size-dependent mechanics for weapons would be the DMG's guidance for determining the damage for a homebrew monster's attacks. But this is not actually a rule that makes damage or any other weapon property dependent on size.)

The nets in traps aren't necessarily the same as thrown nets

Just because some traps deploy nets that cover 10×10 areas doesn't mean that a net wielded as a ranged weapon covers the same area. Nets come in many shapes and sizes, so the nets built into traps that are set up ahead of time can be custom designed to cover the desired area. Such nets are likely too large to wield effectively as thrown weapons. As a martial ranged weapon, the kind of net thrown by a creature can only be thrown at and hit a single target. (If it helps, imagine that the limiting factor is not the size of the net, but rather the difficulty it throwing it in such a way as to spread out over two or more enemies.)

Answer 2

RAW means Rules As Written

Rules As Written is a very specific term. We have a question about it here.

Rules As Written means: you can only do something if there is a specific rule, in the book, which says you can do it.

You can't say "this is what would make sense". You can't say "this is supported by evidence". You can't say "there's no rule that says this doesn't work". All those things might be part of an interesting argument but none of them is part of Rules As Written.

So you're writing things such as:

absent any actual text to such effect, it seems silly to me to presume a mere 5ft net: When have we even seen such a small net depicted or used in actual combat

Thus, it seems well supported that as a weapon, a typical net is 10ft×10ft

Rules As Written explicitly means you don't say things like this. Rules As Written means you go check in the equipment list what size a net is, and if the equipment list doesn't say, then you don't know what size a net is.

In the chat, you're saying things like:

I don't see how a net could possibly be thrown across a 10ft area without having a chance of hitting creatures in that area???

What rule makes you say that attacks targeting a location cannot hit creatures in that location? Attacking a location is allowed, but what gets hit when a location is attacked?

but, once again, this is not how Rules As Written works. Rules As Written means you can't say: "if you can't find a rule that says my thing isn't allowed then you have to admit my thing is Rules As Written!" You can't say: "well, the rules say this is possible but they don't say how, so what's the best ruling for how we should be able to do this?"

Rules As Written means it is your job, as the person who is trying to argue that you can do something, to find a literal rule in the book that says you can do this thing. If you cannot find a literal rule in the book that says you can do it, then it is not Rules As Written.

So, to answer your question explicitly:

There is no rule that says you can do that

Rules As Written means you go check in the equipment list, under the net, and you see if it says: "a net lets you make an attack roll against each creature in a 10x10 area..." and if it doesn't say that then it is not Rules As Written.

And it doesn't say that. So it's not Rules As Written.