What is "Rule Zero" as it relates to D&D 5e? I read How has D&D's guidance to DMs on when to extrapolate from written rules and when to improvise changed over time?, but it only went up to D&D Next.

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    \$\begingroup\$ The question's title seems misleading (causing many to answer just that). It seems that you know what what rule zero is (as indicated by the link you provided), and you are asking about its status in 5e. \$\endgroup\$ Jun 29, 2017 at 19:57
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    \$\begingroup\$ D&D Next and 5e are (generally) the same thing. \$\endgroup\$ Jun 29, 2017 at 20:15
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    \$\begingroup\$ Yeah, let's get some clarification. Most of these answers are just saying what Rule 0 is. Do you already know that? It's really only Rule 0 in 3e, beyond that it's a concept. What are you asking really? If it's "what is rule zero in 5e" - what do you mean? There is nothing called rule 0 in 5e. If it's "what is the guidance in 5e about when to extrapolate from written rules and when to improvise" say that. \$\endgroup\$
    – mxyzplk
    Jun 29, 2017 at 21:52
  • \$\begingroup\$ Also, Rule 0 is also applied to the general rule Have Fun \$\endgroup\$
    – Trish
    Nov 12, 2018 at 12:35
  • \$\begingroup\$ I got to this page searching for what Rule Zero is. These answers are super helpful to me. \$\endgroup\$ Jul 12, 2019 at 3:24

6 Answers 6


Rule Zero, also known as GM fiat, is the common RPG rule that the GM has the ultimate say in all rules matters and can thus introduce new rules or exceptions to rules, or abolish old ones at their leisure. To put simply, it means the GM is like the god of the game. The Rule is commonly used to help ensure the written rules can always be changed to improve the realism, narrative, game balance or other appreciated qualities of the game. However, it may also hurt the game, if the GM applies the Rule in an arbitrary or careless manner.

It should be noted that while Rule Zero has decades of tradition behind it, it is not universally accepted. Many systems such as Apocalypse World have reasonably strict frameworks for the GM to operate inside and recommend house rules to be applied only through the whole group's consensus, although individual groups may still elect to allow Rule Zero.


The exact definition of "Rule Zero" varies, but the general gist of it is "The GM can do whatever he wants." It applies equally to all games, even (or perhaps especially) systems that explicitly recommend against it. The publishers do not have hit squads that go around reclaiming books from people who don't play the game the "right" way.

If the players agree to abide by the GM's rulings, anything goes. If they don't, the GM goes.


What is Rule Zero

What the DM says, goes. Rules in the book are guide posts, but the Dungeon master may choose to ignore, bend or break them to best suit the story and fun of the game. But, by the link you posted I think you already knew that.

As it Applies to 5e

5e has the idea of Rule Zero baked into it. It is stated clearly in page six of the Player Handbook says that the game is played by:

  • The DM describes the environment.
  • The players describe what they want to do.
  • The DM narrates the results of the adventurers' actions.

The DMG also says:

The D&D rules help you and the other players have a good time, but the rules aren't in charge. You're the DM, and you are in charge of the game. That said, your goal isn't to slaughter the adventurers but to create a campaign world that revolves around their actions and decisions, and to keep your players coming back for more! If you're lucky, the events of your campaign will echo in the memories of your players long after the final game session is concluded.


Rule 0 simply put is that the GM is the final arbiter of all things in the game. He/she can change, make up, and remove any rule at any time. Most role playing game systems employ rule 0. Without Rule 0 you're playing (more or less) a simulation game rather than a role playing game.

Rule 0 is probably best embodied in the red box rules for DND: "In a sense, the D&D game has no rules, only rule suggestions. No rule is inviolate, particularly if a new or altered rule will encourage creativity and imagination." Later in AD&D in the DMG from Gygax: "It is the spirit of the game, not the letter of the rules, which is important. NEVER hold to the letter written, nor allow some barracks room lawyer to force quotations from the rule book upon you, IF it goes against the obvious intent of the game. "

As a personal observation the current crops of gamers tend to ignore rule 0 (DMs included) and focus far too much on RAW and RAI. There is this idea the game must be "balanced" (what that means is a mystery to me). The original intent behind rule 0 as I see it is that RAI is whatever the DM intends them to be, not the game designers and not the publisher of the rulebook. Rule 0 implies (and in fact demands) that the game belongs to you and your group of players to develop an adventure narrative.


Rule Zero in 5e is no different in its core interpretation than other versions, and amounts to this:

The GM has final say in all things relating to the game.

Its worth pointing out that this has never really "changed" over editions. Its more a fundamental truth of games that have GMs. What has changed is our ability to recognize it, understand it, and be comfortable with it. No rule has ever stopped a GM from running a game the way they see fit. They might willingly give up control of Rule Zero, or they might be playing a game that doesn't actually have a true GM.

Its called "Rule Zero" because its a rule that players and GMs acknowledge by the very fact of beginning to play a game that has a GM.

As to what it can mean, it really can be anything:

  • A GM can say that no players may play spellcasters in the game they are running.
  • A GM can say that instead of rolling d20s, players will instead roll 2d10 and add them, treating double 1s as "natural 1s" and dobule 10s as "natural 20s"
  • A GM can rule that a character may not attack an adjacent enemy in spite of the rulebook clearly indicating otherwise
  • GMs can fudge any roll they make on their end. GMs roll dice for the sound they make

Now, its an entirely different question to ask how a GM should use Rule Zero, and largely, being able to wisely use Rule Zero is one of the marks of a good GM.


Rule Zero is the idea that the GM has the final word at the table because it is their game.

In 5e, the emphasis on Rule Zero has been lessened vs 1st & 2nd but strengthened vs 4th, and that is, in my opinion a very good thing.

The way I like to think about the rules is that they provide a level of granularity of simulation. This is especially true for exception based rule systems like D&D. A good framework of a simulation allows the players to model the situation and then do fun stuff with the options their characters have. If the players can't model what their characters can do in novel situation, all they will do is that same thing, over and over. Typically that means swing sword until monster dead, etc. Rule Zero can often provide no information about the world being simulated unless you negotiate with the DM in the middle of combat. It can be very arbitrary, and that is a problem.

That is not to say it doesn't have it's place. For example, rule zero is important for resolving conflict, and keeping the game moving. But rules disputes over existing rules are a bit different over DM arbitration on the fly to cover an action that has not rules.

So - In 5e, the game is coming out of a VERY GM AND player constrained game. So the backlash was towards more flexibility and at the table rulings. More go with the flow, let it happen, we really don't need a rule for every situation, feel. So a much coarser simulation than 4e. At the same time, 5e does a pretty good job of not falling back on rule zero as a crutch though.

Contrast that with 1st and 2nd ed that was a little too rule Zero heavy. Rules to accomplish things at the table other than combat were often made up by the GM on the fly. It was grand if you had a good GM, but that was not always guaranteed. There was no chance all rulings would be consistent between DMs - and unless they were codified probably not consistent with the same DM. It was hard for the player to understand what their character could do if it wasn't directly codified in the rules, because coloring outside the lines relied on GM whims.

5e has achieved a pretty good balance, IMHO. The way they have accomplished this is through skills and ability checks - and no other rules. The players now have a pretty good idea what they will be good at doing. But the DM still has some control because they can set the difficulty or decide if the skill check is contested. But the lack of detail surrounding those rules is also important. Basically D&D no longer says something detailed like if you want to intimidate you roll contested check vs. their will and if you beat it by X they run away for d6 rounds; instead 5e still uses rule zero - only with guard rails, if you like

So now the rules are - if the player wants to intimidate pick an appropriate DC and have them roll and then have the NPC react as you like.

On following Rule Zero at the table

It's important to place some trust in the GM. They have done a bunch of work to show you a good time. Sometimes that trust may be taking the hit on a ruling. Even when you know you are "right". Take the hit, and let the game go on. Talk about it after, and if things still don't change say something like "I disagree about how that is intended to work, but I see why you want it that way in your game. Thanks for hearing me out." or something like that.

  • \$\begingroup\$ you're really not going to like DND v.next \$\endgroup\$
    – Jim B
    Jun 29, 2017 at 20:07
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    \$\begingroup\$ Read page 6 of the Player Handbook, and all the statements on twitter by Jeremy Crawford and Mike Mearls that clearly state that rule books are just guides. \$\endgroup\$ Jun 29, 2017 at 20:16
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    \$\begingroup\$ "instead 5e still uses rule zero - only with guard rails, if you like" - Did you read what I wrote? \$\endgroup\$
    – JWT
    Jun 29, 2017 at 21:24

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