GLSL Shaders Mod

GLSL Shaders Mod is the first Shaders launcher ever made. It was created by daxnitro and released on January 6, 2011. The development was ceased in 2012.

It was succeeded by GLSL Shaders OF by id_miner, which was using original source code.

If it is a .n2 file
Any downloaded  file is just an archive file, like ,   or. However, they are designed to be used with Nitrous, a mod patcher by daxnitro.

You should be able to run the launcher, go to File>Import, select the .n2 file, and have the specific mod version appear on-screen. Click "Options" and specify the location of the .jar file you wish to modify. Then click "Local Mods", and "Install Mods".

Theoretically, those are the only instructions needed. I personally could not get this to work on Linux Mint, and have not tested on Windows 10. You may need to download a version of LWJGL 2 (Light Weight Java Game Library) and place lwjgl.jar next to the Minecraft .jar file.

If it is for Beta 1.1_02 or Beta 1.7.3
These two specific downloads are built to require no special patcher.

For the Beta 1.7.3 version, follow the instructions in the .zip file downloaded.

For the Beta 1.1_02 version, just inject the files into your Minecraft .jar file. This can be done by opening it in 7zip, or by extracting the files and later repacking them into a .jar file (possibly also using 7zip). Some other programs have this functionality too, like File-roller in Linux. The idea is to drag and drop the files, replacing the "kr" file with the modified one, and then delete the META-INF folder.

Using Other Shaders
For early versions of the mod, other shaders can be used by once again modifying the .jar file. There are several important files in the Shaders folder inside your Minecraft .jar, which can be modified or replaced with files found on daxnitro's wiki (for 1.0) (for 2.0) or in the forum thread. The rest of the installation follows the same instructions as above.

For later versions of the mod, there may be an in-game shader menu.

Keep in mind however that shaders made for 1.0 and shaders made for 2.0 may not be cross-compatible without modification. Additionally, some shaders may have other compatibility issues due to the nature of using legacy software.

Troubleshooting
Troubleshooting may be done on daxnitro's wiki, or in the forum thread. Alternatively, contact a community member.