A Practical Shader Pack Installation Checklist
Check archive placement, instance folders and pack selection when adding Minecraft shaders.
Find the correct instance folder
Launchers can maintain several separate Minecraft instances. Open the folder for the profile you actually play. Placing a file in the default Minecraft directory will not help if your launcher uses a different directory for that profile.
Keep the shader archive intact
Follow the pack's installation instructions and normally keep its distributed ZIP archive intact. Put it in the shaderpacks folder rather than the mods folder. Avoid nesting the archive inside another folder unless the documentation explicitly requires it.
Select and verify the pack
Open the shader selection screen provided by your loader and choose the pack. Allow compilation to finish before judging the result. If it does not appear, check the archive format, folder location and compatibility before downloading another copy.