Why and How some offline single-player PC games are almost fully moddable while other are not moddable at all ?


Is it strictly a developer decision to allow thier games to be moddable or not ? And how is it achieved ? Are moddable games “coded” differently than non-moddable games ?

In: 4

Moddable games usually have an intermediate scripting language in which the scenarios and behaviors are expressed. It is relatively easy to manipulate and learn through trial and error compared to compiled low level machine code that might also have copy-protection. The script operates on concepts that are closer to what then player sees, such as “move character to these coordinates”, rather than “load value into register A from a memory address”, “multiply it by register B”.

Developers of moddable games may have themselves released annotated examples of parts of their assets, as well as specifications for some internal formats. Games that are not moddable might employ protections to deter hacking, such as checksums and encryption. This could be done because the company wants to profit from selling new content for real money.

It’s like that because if the game is offline – all game files are located on your PC and you are free to change them as you wish.
When the game is multi-player, it requires it to communicate with the server, which you don’t have access to.

Yes, it’s a developer decision if a game is easy to mod or not. Modding is just editing game files. How easy that is for a user is up to developers. They can make the code harder to interact with or not. Sometimes though it requires extra effort to make a game in a way that’s easy to mod, which is why devs don’t always do it.

Another thing though that can massively decide how easy a game is to mod is modding tools. Official tools make modding games much much easier, but again it’s up to the devs whether to release those tools.

Again though, this is often extra work as the official tools they use to create the game are proprietary and can’t be released, so they have to make custom watered down versions to release for modders.

I assume you’re thinking of games like Skyrim. In which case you should know that Bethesda literally provides the modding tools to players and fully supports modding their games. That’s been a thing since Morrowind, and it’s confirmed for Starfield too.

For games where the devs don’t officially support it, which is most games, it depends on:

1. How locked down the games are. As in, things like the encryption used on the files. You need to be able to edit them and still have the game work.
2. How big of a community there is trying to mod it. Stuff like GTA has a lot of mods because of the huge community wanting to mod it.

Ubisoft games are pretty well locked down, which is why there are so few Assassin’s Creed mods, because it’s just too hard to do, despite the large community.

Two big things to have for mods. The first is to make the game with that in mind. As a dev, you have to take decision everytime during the process of making a game. How much money can the player carry? What stats can impact the player? How are weapons configured in the settings?

And if you want people to be able to change something, you’ve gotta make sure that your game doesn’t go up in smoke when new stuff is introduced. Oh, the modder added a new weapons? Integer overflow on damage, thing does nothing. They removed the cap on money? Yay, they can buy the end game upgrade by farming the early bushes for 2h! You need to be so much more careful to prevent mods from breaking stuff too much.

And second: You need to create the tools to mod your own game. Because people will use these tools. So now you have a 2nd program to maintain for modding the game. Which depending on how moddable your game is can be twice the work.

With recent years, a lot of things has changed in particular on the tool side of things. Unity and other powerful game design tools can not only be used to create your game, but also to mod it. Meaning if you decide to make a Unity game, you can just not care about a mod tool and let modders use Unity as well.

All in all, modding is a very powerful way to keep players engaged years after a singe player’s game release (Skyrim, Rimworld, Stellaris, Crusader kings 2/3) but they require extra work to produce. They can also eventually make you the enemy of the community if you’re not careful. If the game works and some very impactful mod exist, people could be angrier at the dev for making more content if it breaks their mods rather than happy to see more stuff. It also mean that if you’re not good or fast enough, mods will develop your game faster than you can keep up with and any update you can make will be redundant leading to reduced sales.

Example of this: Rimworld. The latest DLC added the ability to control machines, control the genetics of your characters and have children. All things that were already available in mods for more than 2 years. Sure the implementation was not the same, but Pawnmorpher, birds and bees and what the hack did all that. Fortunately for Rimworld, it’s an absolutely amazing game and the devs at this point know that they should focus a lot on sturdy mechanics than plentiful content as the modders will do the rest. But not all game will see it that way.

Bethesda is the opposite side of the coin. Where every single update they made for Skyrim is seen as a personal attack by half the community because it breaks so many impactful mods, many of which the author has long left and did not leave the source code available. These mods are forever dead forcing players to chose between not upgrading and keeping their nice old mod they love, or upgrading and enjoying the new stuff.

Mods are great, but they’re a headache and if you’re not careful, you can lose control of it. And it’s a lot of work to get working.