I'm a doctor, not a mechanic
From Unreal Wiki, The Unreal Engine Documentation Site
There seems to be lots of confusion as to what the difference between a mutator, mod, gametype, or total conversion is. You'll find that the definition varies from person to person so the following definitions will probably not be accepted by the whole community, but they should help mod developers.
- Mutators are one way of making a mod activatable for the user. A mutator usually is a small modification to only one or few rules of a game, but there are exceptions to this rule. Mutators are usually made with the intent for it to be compatible and/or usable with other mutators, most game types, or even multiple game types or total conversions. A mutator has rules governing how it should behave, how it should interact, and how much it should change within a game. See Mutator Topics.
- Gametypes are another way to make a mod user-selectable. Each gametype has a different objective. The gametype of CTF is Capture The Flag. The goal is to find and return the enemy flag to your base. Included with UT2K3 is also the gametypes of BR (Bombing Run), DM (Deathmatch), TDM (Team Deathmatch), and DOM (Domination). Each gametype has a different way to end or win a map.
- Total conversion (TC)
- A total conversion is a collection of gametypes with a common theme and purpose. For a total conversion it is generally accepted that new menus will be present, new graphics will be used throughout the entire game, a new set of INI files will be used, and that little, if any, content from the original game will be present or used.
- Server add-on
- Server add-ons don't change any part of the game's rules. Usually they add additional features for remote administration, security, player stats, etc. Server add-ons are often activated by adding an entry to the ServerActors list (INI section [Engine.GameEngine]), but there are also other ways, like changing the AccessControlClass (INI section [Engine.GameInfo]) or adding WebApplications to [UWeb.WebServer].
- Client add-on
- In UT's UWindow system it was possible to use some client-side add ons like GUI skins or other game menu modifications like the Mod Menu Extension or [osX] Background Changer. These not change any part of the gameplay, but only help players like their favorite game's menu system. ;) Client-side add-ons aren't possible in UT2003 anymore. (At least not at this time.)
- New content
- Maps, voice packs, announcer packs, player models or skins and similar content additions could also be viewed as mods since they modify and extend the game.
Note that the term "mod" does not appear in this list, because it only is a general term for all kinds of modifications to the game. Players often distinguish between "mod" and "mutator" eventhough they are actually only refering to different mutators.
Here on UnrealWiki we try to keep the term "mod" for the general concept of a modification to the game. A "mutator" is anything that can be added through the mutators list, while a "gametype" is anything that is activated through the game type list. There are mutators and gametypes that come with the game and there are custom mutators and gametypes – the former are stock content while the latter are "mods", no matter how much they actually do.
 The Layman's Guide to Making Mods
If you are thinking about making a mod (for any game) and are not sure what you need to know, how to go about it, or simply want to avoid the most obvious mistakes then read on. The pages linked to below contain some excellent advice, and possibly comments on stuff that hadn't occured to you.
- Legacy:Making Mods/My_Team_Your_Team – Introduction and disclaimer for all those, "what's all this my team your team crap?" readers.
- Legacy:Making Mods/Why_Are_You_Making_A_Mod – Sometimes the reason a mod fails is the reason you started it in the first place.
- Legacy:Making Mods/Building_a_Team – Building up your mod team.
- Legacy:Making Mods/Despotism_Or_Communism – Some thoughts on team structure.
- Legacy:Making Mods/Working_as_a_Team – The day to day life of a team.
- Legacy:Making Mods/Asset_Management – How to manage the assets of your mod (code, textures, models, etc).
- Legacy:Making Mods/Distributed_Development – Find out how hard and unpleasant distributed development can be.
- Legacy:Making Mods/Effective_Testing – How to get the most out of testing your mod.
- Releasing A Mod
- Legacy:Making Mods/Supporting_Your_Mod – Easing the burden of mod support.
- Legacy:Making Mods/Mod_Death – What happens when a mod or mod team self destruct and how to cope.
 Thoughts on Mod Making
Several of the Unreal Wiki's contributors have experience in creating successful mods. Reading their accounts of their work and their advice is recommended.
- Mychaeel/Mod Startups – Making your idea a reality.
- Mychaeel/Modding Etiquette – How to make people like your mod.
- Jb – an analysis of the ChaosUT mod's history
- Piglet/Finishing_Things – How to actually finish your mods, that said it's more how to start so that you can finish.
- GODZ_Inception – a journal of how GODZ started.
- Making Mods/General Mod Optimization – Common mistakes and ignored settings which often lead to lower performance – and how to fix/use them.
 Some Recommended Reading
It never ceases to amaze me how many programmers completely fail to take advantage of the wealth of experience of software developers that have decided to commit the things they have learnt to paper and write a book. Although the following books will not help you write mods, they will help you write better software, and possibly manage your team and project more effectively. You don't have to agree with what the books say – as long as you understand why you disagree. The books are in no particular order. (the links go to the original Wiki at C2: Wiki:WelcomeVisitors, which has plenty on coding and is also a recommended read.)
- Wiki:CodeComplete – by Wiki:SteveMcConnell
- Wiki:RapidDevelopment – by Steve McConnell
- Wiki:DebuggingTheDevelopmentProcess – by Wiki:SteveMaguire
- Wiki:WritingSolidCode – by Steve Maguire
- Why Teams Don't Work – by Harvey Robbins and Michael Finley
- Peopleware – Productive Projects and Teams – by Timothy Lister and Tom Demarco
 Books on Unreal Modding/Programming
-  - Mastering Unreal Technology: The Art of level Design
-  - Unreal Tournament Game Programming for Teens
-  - UnrealScript Game Programming: All in One
 Related Topics
 Basic Topics
 Design Concepts
 Modding Topics
- Brandon Reinhart's Mod Authoring. Written in the early days of UT, but much is still relevant.
- Mod_Authoring_for_UT2K3. Document similar to Brandon's but for UT2K3.
- Interactive GUI
- Maya PLE Character Model Tutorial - A tutorial covering modeling, animation and import of skeletal mesh characters
- Category:Legacy Custom Class - A list of custom classes on the wiki
- Unreal_University - An annual weekend seminar given by Epic (and others) on the topics of mod making.
- Mod Ideas - Get some ideas for a project or share your own
- Testing Lab - Get others to help test your code
SuperApe: This page deserves to be linked from the Home Page. Is this a good hub for Modding?
fleshsniper1: hmm.... iv looked around and all this wiki gives on making mods is opinion/experience. it doesnt tell you where to began if you actualy want to start making one. like in SOURCE engine, they tell you that you must first get a base by copying some of the codes and then you start editing the menus and create a map and such. now for me a newb, im not sure where to start. do i just make maps and replace some models and edit the scripts? how would i make menus and where do put my content source? i guess im talking more on a TC mod which i believe requires more than what is provided here... thanks for reading
Ambershee: There are loads of tutorials on the wiki. Look at the sections Mapping Lessons and UnrealScript Lessons.
fleshsniper1: right now iv done most of the basic tutorials. i can make a crappy map and compile it with pawn actors and such basics. but where do i began creating/importing content and maintining my content away from unreals content. how to go about? is that what packages are for? it would be nice if there was a guide for making a SP mod that includes starting up a base that wont interfere with the UT2004 game, how to manage content. somthing like that :)
fleshsniper1: Well hello. I will tell you that your mod will never work or even get of the ground, if you dont know how to script. No matter how good your design or artist you are, whatever great ideas you have, they will never get of the ground or come to fruition until you learn to script (or posses scripting ability through another person) which is basically programming. I realize my low inspiration was due to this fact (and real life issues lol), I always though i could become a scripter later on and can work on the art first, but now i realize it is unhealthy... 1/5/08, Now iv tested all parts of developing games and i know what i CAN and cannot do. I can make any games i want :), thanks to the great flexible unreal engine 3... I just hope the NWO and other bad people dont start enslaving humans before my game is complete. After my game is complete i have no worry
computergod666: Anyone know if it is possible to do a singleplayer mod for UT, and how?
Raven: It is possible to make a single player mod. It is just a gametype, but the rules are explicitly setup to focus on the single player aspects. There are many extra issues that come up when making an exclusive single player game, mostly to do with the shear output of art content to give the player enough to do and see.
computergod666: Thanks. So does anyone know of a good tutorial for making SP mods?
computergod666: I get the funny feeling that no one around here is interested in single-player games!
SuperApe: Old Skool Monsta Toolz can help for UT2004. OSM Adventure is a single-player/coop gametype and OSMT gives you plenty of tools to make a SP adventure in UT2004. And of course, if you're talking about UT99, there are the original "old skool toolz" availble there. :)
Wormbo: UltraHyperCode, people keep deleting this because it doesn't make much sense and definitely doesn't belong on this page. Delete reply when you see it.