Full 'link'bright 1.8 Site

If you use Minecraft Forge for version 1.8.9, you can install a dedicated mod for more control. Download a mod like Fullbright v1.0.0 from Modrinth. Place the .jar file in your .minecraft/mods folder.

During this era, the distinction between "cheating" and "quality of life" blurred. Client modifications like Labymod, Badlion Client (later), and various hacked clients integrated Fullbright as a standard feature. In 1.8, the easiest way to achieve this was often by modifying the gamma settings in the options.txt file or using a resource pack that removed the overlay textures for darkness. fullbright 1.8

I notice you're asking for "fullbright 1.8" — likely referring to a Minecraft client mod or gamma override for version 1.8. If you use Minecraft Forge for version 1