Foreword

This is quick update for 2020 of my ROM hacking guide, a guide that I have been writing on and off for several years at this point. This version is a continuation of the 2012 edition which itself was almost a complete rewrite of earlier efforts and is mainly to fix a few broken links. Not a lot has been added since the 2014 or 2016 updates which were mainly there to update a few links. A guide was first attempted a little under a year after I decided to take up ROM hacking in earnest, a period which coincided with the rise of the dedicated DS flash cart. Give or take some fiddling with PC games many years before my first real in was probably learning to shrink ROM images to fit on GBA era devices that were not built to cater with file sizes seen in commercial DS titles. The first version was little more than collections of forum posts I made on various subjects and short overviews of the areas aiming to point people in the right direction if they wanted to learn how to do something, the later versions aimed to teach people some of the underlying principles and this continues along that path.

At one point there was a sister document aiming more at hardware and device hacking, various parts were merged into this but for the most part that project was put on indefinite hold. Beyond that it might be considered outside the scope of this document, however it is far from unusual to see people with serious electrical and mechanical engineering skills become accomplished ROM hackers as the thought processes and mentality tends to fit in well.

I have always pulled things apart and poked around in directories of programs in an attempt to see how they tick or tweak them to my liking. As far as ROM hacking is concerned the turning point came when I decided if something did not reveal itself via superficial means (plain text or some minor markup, double clicking the files and maybe a quick search of the program/extension) then I would attempt to drill down into it to figure it out. It soon occured to me that this would require knowledge of how things work from the ground up (or close enough to it) so that became what I sought to do. This was the start of an ongoing process I have been able to apply in many aspects of life and has instilled a mindset that continues to serve me well.

Countless sites, hackers, conversations and tools have gone into getting this document and the author to this point but special mentions go to the DS ROM hacking section of GBAtemp, romhacking.net and anybody I have held a discussion with on those sites, cearn who authored the GBA programming tutorial Tonc and Martin Korth who is the author of the no$gba specifications, though they detail very little of direct use to a lot of ROM hacking it can easily be said that most of present GBA and DS ROM hacking would not have got off the ground without them. Last but not least those responsible for the Crystaltile2 program that ties together several nice tools into a single program which allows me to tear about the ROM images at breakneck pace in a manner, one that would be hard to do using basic tools, and indeed it took until 2011 for us to see other tools that rank up there with it, when attempting to figure out how a ROM works.