Core shaders: custom HUDs and minimaps without mods

Most players will never install a mod to join your server. Core shaders get around that: they ship inside your resource pack and change how the vanilla client draws the game, so players get custom visuals just by accepting the pack.

What core shaders are

Since Minecraft 1.17 (Java Edition), a resource pack can replace the shader programs the game uses to draw text, items, the GUI and the world. These are the "core shaders". They aren't the same as OptiFine or Iris shader packs: those need a mod, while core shaders run on the plain game.

What servers use them for

• Custom HUDs: health, mana or stamina bars in your server's style.
• Minimaps and compasses drawn on the screen.
• Screen effects: damage flashes, fades, vignettes, transitions.
• Animated menus and GUI elements.
• Hiding or restyling vanilla elements you don't want players to see.

How the shader knows what to draw

A shader can't talk to your server directly. The usual trick is for the plugin to encode values in something the client already renders, such as the color of a piece of text or a special character from a custom font, and for the shader to recognize that marker and draw the right thing instead. That's why core shader work is usually a pair: a resource pack and a plugin that feeds it.

Limits to know before ordering

• They are tied to the game version. Mojang changes the shader files in some updates, so a pack is built and tested for your server's version.
• Some client mods render parts of the game their own way (performance mods like Sodium, for example), so test with the mods your players actually use.
• Everything happens on the player's GPU, so effects should stay light to keep low-end players happy.

Done right, core shaders are one of the cheapest ways to make a server look like nothing else. My vanilla minimap project, built only with a resource pack and core shaders, is a good example of how far they go.