Some retro games are moddable by design (have built-in map editors), others were disassembled long time ago and their level formats decoded, and custom editors created, others just have their source code published, which makes it easier to decode the format of resources inside the game executable.
But what makes a game completely unmoddable for years?

Examples: The Lemmings; The Lost Vikings; F-19 Stealth Fighter

  • 9
    Lemmings on which platform? It's on everything from Commodore 64 up to in-browser using HTML5. The other two games are similar. Is there any discussion as to them being un-moddable or is it just a case that there's no demand for it ?
    – Alan B
    Commented Sep 27, 2022 at 8:01
  • @AlanB the fact 'Lemmings' was ported to multiple platforms only tells that there is high demand for it; many thousand people would enjoy new levels and new tools (perhaps adapted from Lemmings 2) for their favorite game; 'Lost Vikings' is listed on the shikadi.net website as unmoddable, which indicates there is as much demand for it as for the 'Commander Keen' series
    – ivan866
    Commented Sep 27, 2022 at 14:35
  • @AlanB 'F-19' was re-published on Steam distribution platform several years ago, which indicates there is demand for it; however, there is somewhat about 99 missions in it, hard-coded, and the game is still playable - given new warfare regions and new missions can be provided
    – ivan866
    Commented Sep 27, 2022 at 14:38
  • 6
    @ivan866 I don't see anything on that page saying it's "unmoddable"; on the contrary, it has some investigation details that would be useful for someone trying to work on a mod. There is a category on that wiki called "unmoddable", but all it seems to mean is "nobody's got round to working out a modding strategy for this game yet". The category doesn't contain any of the 3 games you list in the question.
    – IMSoP
    Commented Sep 27, 2022 at 15:12
  • 2
    @user3840170 being on a ROM is no issue, since the data can still be extracted and emulated. There a ton of games unreleased outside of Japan that were given fan translations and some(I remember the most popular Tales of Phantasia fan ROM changed some of the sprites to include a bit of 16 bit nudity as well as changing some of the dialog to be raunchy)
    – Eugene
    Commented Sep 27, 2022 at 16:43

2 Answers 2


No game is unmoddable. However there's a few reasons the barrier-to-entry might be higher for older games:

  • Lack of interest. Most people are interested in playing newer games. Older games, especially niche ones, have a much smaller audience.
  • Specialized hardware knowledge. Most modern games are playable on x86 (Intel) architecture. However most older consoles had their own CPU architectures. Modding games for these consoles requires knowledge specific to that console. This also means modders may need to write their own reverse-engineering tools.
  • Natively compiled code. Nearly all older games were compiled to native machine code, which tends to be a lot of work to reverse engineer. Many (but by no means all) modern games are written in languages like C# or Java, which are compiled to intermediate languages; or have their logic written in a scripting language like Lua. Both cases make the game much easier to reverse engineer.
  • Modern gaming engines. Most older games used game engines that were specific to that game, or at best, that development studio. Most modern games use one of only a handful of engines (usually Unreal or Unity). This allows modders of different games to share knowledge and tools with each other, again lowering the barrier-to-entry.
  • 14
    Another barrier can be DRM systems. The same technology which prevents changes to the executable which circumvent copy protection often also prevents any other change.
    – Philipp
    Commented Sep 27, 2022 at 10:36
  • 26
    And then there are server-sided components which run on the servers controlled by the developers. The user can't mod what they can't access.
    – Philipp
    Commented Sep 27, 2022 at 10:38
  • 7
    @RobinClower Did you mistype there? Wikipedia says it was almost entirely written in assembly language, which would indeed make reverse-engineering harder than some technologies (most flavours of BASIC would be on the easy end of the spectrum, as they're not even compiled). On the other hand, people have modified console ROMs without even a disassembler, just reading raw hex machine codes - for instance, see this wonderful article about fixing the notorious Atari ET game.
    – IMSoP
    Commented Sep 27, 2022 at 14:18
  • 6
    Another thing: in modern code I can expect map / character / graphic data be neatly bundled together with some kind of logic. In old games, a few cycles were more important than clear code, so you can get enemy generation data within camera moving subroutine, id means different things in different moments, bunch of spececial cases where unrelated things happen to trigger something in another part of code... Commented Sep 27, 2022 at 15:31
  • 9
    Many (but by no means all) modern games are written in languages like C# or Java Some games might indeed be written in C# thanks to Unity especially, however Java is very rare (yes I'm aware of Minecraft). Most games still get written in C++.
    – Thomas
    Commented Sep 28, 2022 at 12:06

Another big thing that might trample any kind of modding, ESPECIALLY if it's an actively updated game, or fairly modern, is anticheat software. While yes, most anti-cheat systems have been circumvented in the past, a modern anticheat will also update itself with the internet and can make it difficult, or even impossible to mod until the developer of the anticheat stops, even if the developer of a particular game stops with it.

The points listed by BlueRaja above also make a good point, but if there's a giant corporation making a game and/or console (Nintendo) they can actively make it harder to mod a game just by making constant patches.

Again though, with enough dedication from a community, anyone can get through the barriers, so really the biggest point (again, from BlueRaja) is that there is no active will to mod it.

  • 1
    Anti-cheat software is one reason why, for example, Genshin Impact doesn't have mods despite being a hugely successful title with a very creative community and being developed on a very well-known game engine (Unity).
    – Philipp
    Commented Sep 28, 2022 at 11:30
  • 5
    @Philipp Genshin actually does have a thriving private server community. I'd categorize private servers as mods.
    – nulldev
    Commented Sep 28, 2022 at 17:44

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