How to install Minecraft Mods with the New Launcher (1.6 and up)
Today I wanted to share a brief tutorial of how to successfully play a modded Minecraft in the new launcher. As many of you know, Mojang is currently working on a new and improved launcher that allows for automatic updating, quick switching to and from multiple versions, and future modding API support. So far the one downfall of this new launcher is that it will automatically download new files if you modify your client in any way. After some experimenting however, I found a way around this. This method will also allow you to save older versions of Minecraft which you can play at a later time through the launcher
First let’s take a look at the new .Minecraft folder structure:
Next go into the “versions” folder. Here we have all the different Minecraft versions that you have downloaded from the launcher so far.
Step 1: Make a copy of the version you want to mod or save. I renamed it “CUSTOM” for this tutorial.
Step 2: Next, rename both of the files inside to the same name that you named your folder. In this case it will be “CUSTOM”.
Step 3: Next open up your CUSTOM.json file in a text editor (Example: Notepad++) and edit the “ID” line to match the name of your folder.
Step 4: Lastly, open up the launcher and you will now see your custom Minecraft in the drop-down menu. You can add whatever mods to it you want (like optifine) and they will not be copied over each time you launch Minecraft
Or watch these videos: