It seems that questions about whether (and if so, to what extent) GameMaker: Studio games can be decompiled are being asked at a constant pace, and yet there are still no resources to clear up these questions. So I've decided to make a small post on the matter.

If you are not familiar with what is this all about: older versions of GameMaker had produced executables that could be reversed into an editable file with a help of a program ("decompiler"). Such unpleasant turn of events was made possible because:

1. Game data was more or less just appended to the end of a "runtime" executable
2. Source code was inserted into data as text, with code structure and comments intact.

So a program would "read" the appropriate sections of the executable, extract game data, and repack it into an editable file, permitting various acitivities, most of which would violate EULA.

To mention, a lot of Lua-based game engines also suffer from this kind of problem, and it is generally solved by obfuscating source code and altering the executable structure (in GM's case, with a so-called "anti-decompiler") for the "decompiler" to not even be able to extract the obscured game data as easily.

So it's a valid thing to wonder about how much of this still applies to GameMaker: Studio...