MCPatcher is a program that patches Minecraft so it can support higher resolution texture packs than the game's default 16x16. It also adds support for custom lava, water, and portal animations. Version 1.x of MCPatcher could only patch the game to support a single resolution at a time, and had limited support for switching between texture packs within the game. Version 2 allows you to switch between any size texture pack on the fly.
Start MCPatcher by double-clicking the jar file. The main window should appear:
If you've used MCPatcher before, the first thing you'll notice is that
there's place to select your texture pack. That's because you no longer need
to. Place all your texture packs no matter the resolution into the
<minecraft dir>/texturepacks folder and choose between them
in-game.
In the simplest case, all you need to do is press Patch and wait for it to finish. Then, pressing Test Minecraft will launch the game in single-player mode. For multiplayer, run Minecraft via the launcher as usual.
The Browse buttons let you select a different input or output jar. MCPatcher automatically finds your Minecraft installation, so you should rarely need to use these.
Unpatch will restore Minecraft to the state it was in before the first time you ran MCPatcher. If you had other mods loaded before MCPatcher, they will still be there. If you loaded them after running MCPatcher, you will need to reinstall them. Unpatch also resets Minecraft to the default texture pack. This is because an unpatched Minecraft will crash on texture packs larger than 16x16.
The Mods window lets you enable or disable individual mods. If a mod is greyed out, that means it is not compatible with your version of Minecraft. This could mean an update came out that broke MCPatcher, or you have a mod conflict that MCPatcher cannot resolve.
The Log window gives detailed information about what MCPatcher is doing and lists any errors that occur.
The Class Map and Patch Summary windows give detailed information about Minecraft and the patching process. This is mostly useful for troubleshooting and to mod developers.
If you are using other mods, it is best to install them before running MCPatcher. MCPatcher does its best to work with other mods you may have installed. It is designed to change only certain parts of the code and leave everything else alone. If you have other mods installed, MCPatcher will warn you that there may be problems, but it will attempt to continue.
It is possible to install other mods after running MCPatcher, but only if they do not replace any classes modified by MCPatcher (see the Patch Summary window for a list). If another mod overwrites a class that MCPatcher has patched, Minecraft will almost certainly either fail to launch entirely or crash shortly after startup.