Resource packs

Iris Shaders: GLSL Source Pre-Processing Failed

What the log looks like

java\.lang\.RuntimeException: GLSL source pre-processing failed
JcppProcessor\.glslPreprocessSource\(JcppProcessor\.java:

How to fix it

  1. Open .minecraft/logs/latest.log and look just above 'GLSL source pre-processing failed' for 'Failed to load the shaderpack' to confirm which shader pack file caused the failure.
  2. Update Iris (or Oculus) and Sodium (or Embeddium) to the latest release available for your Minecraft version, as newer Iris updates include fixes for strict GLSL preprocessor parsing.
  3. Update the failing shader pack to its newest version from Modrinth or CurseForge, and re-download the .zip file to rule out a corrupted download.
  4. Delete the matching shader settings file inside .minecraft/shaderpacks/ (the .txt file with the same name as your shader .zip) to reset any custom shader options that may be activating broken macro code.
  5. If the shader pack still fails to load (common with older or unmaintained packs like Chocapic13 Toaster Edition), switch to a modern Iris-compatible shader pack.
LoadersFabric, Quilt, Neoforge, Forge
SeverityBreaks something
CategoryResource packs

Check your own log

Related errors

Resource packsCompletionException: RuntimeException: could not reload shadersOpen logs/latest.log and scroll below 'could not reload shaders' to find the 'Caused by:' line (typically ShadResource packsMinecraft Failed to Reload Core Shaders (could not reload shaders)Disable active resource packs that modify fonts, UI, or core shaders; if the game crashes on launch, open optiResource packsResource pack could not be loadedCheck pack.mcmeta — pack_format must match your Minecraft version