Shaders in 1.12.2 introduced specific visual traits that defined the "look" of that era's YouTube content creation.

Inside the shader settings (Shaders > Shader Options > Shadows), drop the shadow resolution from 2048 to 1024 or 512. You will barely notice the visual difference, but your FPS will double.

Before diving into the shaders themselves, you might wonder: Why should I use 1.12.2 instead of 1.20 or 1.21?

The answer is Mod Compatibility. 1.12.2 is the golden age of Forge modding. You can run massive tech mods (Thermal Expansion, Ender IO), magic mods (Thaumcraft, Botania), and exploration mods simultaneously. When you add shaders to this mix, you don't just get a pretty game; you get a next-gen RPG experience.

Furthermore, many shader developers perfected their code during the 1.12.2 era. Unlike later versions that rely heavily on Render Dragon or complex PBR textures, 1.12.2 shaders are mature, stable, and highly optimized by community standards.

To understand shaders in 1.12.2, one must understand the vehicle that delivers them: OptiFine.

Despite Minecraft Java Edition currently being on version 1.20+, a significant portion of the shader community remains on 1.12.2 for two reasons:

Once inside the game:

Forge + OptiFine works fine, but manually install OptiFine as a Forge mod: