Installing Minecraft Forge

Run the version of vanilla first

Forge installs on top of a Minecraft version that already exists on your computer. Before you run the installer, open the official launcher and play the matching vanilla version once, then quit. That one step avoids most "the installer finished but nothing happened" reports, because the installer needs the vanilla files it is patching to already be downloaded.

Running the installer

Forge ships as a single .jar installer. Double-click it and you get a small window with a few options; the one you want is Install client. Leave the folder path alone unless you deliberately keep Minecraft somewhere other than the default. Press OK and wait for it to finish.

If double-clicking opens an archive manager instead of running, Java is not associated with .jar files on your system. Installing a current Java runtime and opening the file with it fixes that.

Picking the profile

The installer does not launch anything. It adds a new profile to the official launcher. Open the launcher, go to the installations list, and choose the entry with Forge in its name before pressing Play. If you press Play on the vanilla profile, you get vanilla — with no mods and no error, which is exactly why this step gets missed.

You know it worked when the main menu shows the Forge version in the corner and a Mods button appears below the usual buttons.

Servers

A server needs its own install. Run the same installer and choose Install server into an empty folder, then start the server jar it produces. The server and every player connecting to it must be on the same Minecraft version and the same major Forge version.

What Forge does and does not do

Forge is a mod loader. By itself it adds no items, no blocks and no gameplay — the main menu will look almost unchanged. Everything new comes from the mods you add afterwards, which is the next step.