This is an editorial. It is not covered by the Open Gaming License.

One of the things that’s being debated in the wake of the “One D&D” playtest release is how this is going to impact D&D customers, other publishers making compatible products, Virtual Tabletops (VTTs), and the ttRPG environment overall. For better or worse, D&D has a huge influence on tabletop RPGs overall in the English-speaking world. Even if you don’t play D&D, and never have, it’s popularity can impact what dice, maps, digital tools, play spaces, game conventions, and dozens of other adjacent materials and options are available to you.

There have been sea-changes in what was considered “D&D” several times before. The release of AD&D in the late 1970s was one, and to some extent so were both BECMI and 2nd edition AD&D. The release of 3rd edition in 2000, which dropped the “advanced” in the title, along with the introduction of the d20 System and OGL had a huge impact in 2000, and the release of edition “3.5” in 2003 is seen as going hand-in-hand with the “d20 crash,” leaving a lot of companies who used the OGL in trouble. (Indeed, many ceased to exist, and others walked away from d20 System-derived games forever.) Similarly the release of the radically different D&D 4th edition in 2008, which abandoned the OGL, had significant impacts throughout the industry (not the least of which was the creation of the circumstances that lead to Pathfinder 1st edition, and by extension eventually Starfinder and Pathfinder 2nd edition).

With the exception of the switch from 3.0 to 3.5, these changes didn’t much revolve around claims that the new D&D would be compatible with older editions. The release of 5e in 2014 was a bit different, often centered on the idea that it was going to take the best ideas from all previous editions, but it also tied to efforts to be simpler and more accessible, and to have “bounded accuracy” fix many of the problems in mid- and high-level play.

One of the talking points of One D&D is that this isn’t a “new edition,” but a modification of the once-and-future D&D engine that is the core of 5e. It is, we are told, going to be compatible with existing D&D materials.

So, in this instance, what does “compatible” mean? And, what’s WotC’s goal in striving for their new rulebooks (I’m entirely convinced there will be new print PHB, DMG, and MM books, and that belief serves as one of the underpinnings of this analysis) to be in some way compatible with the material they have been putting out since 2014?

Well, firstly, I don’t expect WotC to be particularly concerned about how their decisions impact people making “5e Compatible” products, and I don’t think it’s realistic (or, honestly) reasonable for anyone else to expect that either. The only group that might feel they have some claim on WotC’s mindspace is Dungeon Master’s Guild publishers, since they are working within the WotC IP, in a space where WotC gets a cut of their income. But even then, I personally expect WotC to do what they think is best for their own company (and will thus be most likely to allow them to continue to be the best-paying ttRPG employer in North America, and maybe the world).

My best guess is that WotC is going for One D&D to be “100% Adventure Compatible.” And, in this, I may be letting myself be influenced by the fact that’s very similar to what I was shooting for in the Fantasy Age Core Rulebook, which I have been saying since its inception was not a “new edition,” but a “quality of life improvement implementing much of what we have learned since Fantasy Age Basic Rulebook came out.”

While working on that, I discovered that you can make a new rulebook be “100% “compatible” with all the old accessories and adventures, and still not be exactly the same game. You can, with skill and caution, make a game with some new mechanics, and some mechanics that work differently, and not create anything that doesn’t work with the old game mechanics.

Let me give you a concrete, and entirely theoretical, example.

Let’s say you had S.T.A.B. (Sneaking, Talking, Arcana, and Battle) 1st edition, a very d20 System-esque game, where the success of most tasks are determined by rolling a d20, and adding some modifiers, and trying to hit or beat a target number. If you d20 die roll is a natural 20 you automatically succeed, and if it’s a natural 1, you automatically fail. And, one of the persistent pieces of feedback you get, is that people hate Hate HATE rolling a 2 on their d20 roll, because they will always fail due to the game math, even though it’s not an “automatic failure.”

So, when you release S.T.A.B.B.E.D. (Sneaking, Talking, Arcana, Bards, Battle, Economics, and Dragons), an “updated rulebook for S.T.A.B., you add a new rule — anytime your d20 roll is a natural 2, you then roll 1d10 and add it to your total. If you roll a 3 you add 1d8, if you roll a 4 you add 1d6, and if you roll a 5 you add 1d4. (This is almost certainly a terrible rule, I’m using it just as a very basic illustration of “compatible-but-not-the-same’).

Now, this changes the math of the game, and impacts how the game plays in many significant ways. Someone playing with the S.T.A.B.B.E.D. book is going to have a very different experience than with the S.T.A.B. book, and you can’t really have some players use one and some use the other. But you CAN use *either* to play through the classic adventure “King of the Demonpit Webs.” And they both work with the official expansion Stabinomicon book of extra classes, ancestries, spells, and talents.

But if a third-part publisher had released BASH (“Basic Adventure System Handbook”), based on STAB, and in BASH there was a whole system for earning a “booster die,” which you added to d20 rolls, and additional rules written with notes such as “If either your d20 die, or any die you get to add to it, is a 1, you take a point of Dangit, which the GM can use to cause you bad luck,” then the BASH system suddenly isn’t nearly as compatible with STABBED as it was with STAB.

Now, that example is clearly and intentionally ridiculous. But it shows how a new rulebook can have a set of notably different game rules that still work with all the official expansion books a company has released. It is, in that regard, “compatible.” And for people who only but official STABBED books, it doesn’t matter if they play older adventures or newer “Hardship paths,” though old STAB books, and anything other publishers build off STAB, may not work with all the new material.

While obviously I don’t have any insider insight into exactly what WotC is planning beyond what they have publicly stated, I have done this kind of backwards-compatible new game book work myself. It can be done. And it’s compatible.

Just not the same.

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