The tools you'd need to make a mod depend on what you want to mod.
Image Editor[edit | edit source]
If you want to edit image files, you'll need something capable of editing .tga or .png files (GIMP, Photoshop or even Paint will do).
Text Editor[edit | edit source]
If you want to edit or add game data, you'll need a plain text editor (like Notepad or Notepad++, but NOT Microsoft Word or other formatted text editors).
StringWrangler[edit | edit source]
If you want to edit or add game strings (usually necessary when adding new objects to the game, can also be helpful to give your mod a title and description), you'll need StringWrangler, a Longbow-developed tool downloadable from https://pub.longbowgames.com/StringWrangler.zip.
FiatXML[edit | edit source]
To overwrite the .fi files used in the default sandboxes, you'll need https://pub.longbowgames.com/misc/FiatXML.zip to decompress them into hand-editable formats or compress XML files into .FI files. (be sure to use Tools->Re-Indent when exporting to .xml and the two other tools when exporting to .FI). Note that this is only necessary to change existing sandboxes, as new ones can be left in .xml format.