How do Minecraft mods or resource packs contribute to the '1 code error'?

Incompatible, outdated, or corrupted mods and resource packs are frequent causes of the '1 code error'. If a mod is not designed for your specific Minecraft version, conflicts with other mods, or has corrupted files, it can prevent the game from loading. The same applies to resource packs that might alter game assets in a way that causes instability. To diagnose, try launching the game without any mods or resource packs (or in safe mode, if using a mod launcher) and gradually reintroduce them to identify the problematic one.