If you are open to installing a mod but still want to avoid OptiFine, consider —a simple Minecraft mod that increases brightness in dark caves, nighttime, underwater areas, and other low-light environments without requiring OptiFine.
Change the value from 1.0 (or whatever number is present) to 16.0 . Save the file and restart your game. Dimensions Still Look Dark (Nether/End)
I can provide direct links or walk you through advanced configuration tweaks based on your goals. Share public link
"Fullbright" is the common term for making Minecraft's world appear fully lit, eliminating shadows and darkness. It's a massive help for navigating caves, building underground, or just avoiding mobs in dark areas. This effect tricks your game into rendering every surface as if it were at a light level of 15, providing perfect visibility. Yes, there's a potion of Night Vision, but that's temporary, while a fullbright texture pack gives you a permanent effect.
Manual install steps
Navigate to Options -> Resource Packs . Open Pack Folder: Click on Open Pack Folder .