ALLOWED MODIFICATIONS:

- Optifine / Shaders
- Armor Status / Effect Status / Damage Indicators
- Rei's Minimap / Replay Mod
- F3 + B
- Toggle Sprint and Sneak
- Printer / Schematica

DISAPPROVED MODIFICATIONS:

- Hacked Clients / Autoclickers
- X-Ray / World Downloader
- LabyMod 2.5 and below (LabyMod 2.6+ is allowed)

This is not a complete list! 

Unsure If your modification is allowed?

Ask yourself if it gives you an unfair advantage. If it does, you will be punished accordingly.