Minecraft Launcher

Do NOT disable "API" or "library" mods, because the other mods need them.

1. Open the Minecraft Launcher

2. Select the Fabric installation

3. Click on Folder button

4. Open the mods/ folder

5. Find the mod you want to disable

6. Rename the mod from mod-name.jar to mod-name.jar.disabled

7. If you want to re-enable the mod, rename mod-name.jar.disabled to mod-name.jar

If you can't see the .jar extension in the file name, follow this tutorial to show file extensions.