How to Run OptiFine Shaders on a Fabric Modpack

Install the shader support layer

OptiFabric alone does not add shaders — it lets the official OptiFine jar load on Fabric, and OptiFine is what provides the shader engine. Make sure OptiFabric and the OptiFine jar are both present in your mods folder, then launch the game once so OptiFine can generate its config files. If the game crashes on startup, a conflicting rendering mod (such as Sodium or Iris) is usually the cause; remove it before continuing.

Enable and tune a shader pack

Open Options → Video Settings → Shaders. Click Shaders Folder to open the directory where packs belong, drop your .zip shader pack inside, then return to the game and select it from the list. Apply with the button at the bottom of the screen.

Inside the shader options you can toggle individual effects like shadows, water waves, and volumetric light. If your frame rate drops, lower the shadow resolution first — it has the biggest performance impact. Use the in-game zoom key to inspect distant terrain while tuning, since some effects only become obvious at range. Test in a world with water, foliage, and mobs before committing to a pack, because different packs stress different parts of the renderer.