How to idle monsters safely
For most monsters, you can check by comparing your 
Auto Eat threshold to the monster's max hit. To find your auto eat threshold, tap the Auto Eat icon below your HP bar. To find the monster's max hit, start fighting the monster and look at their "Maximum Hit" in their Offensive Stats box. This number already accounts for the Combat Triangle and your Damage Reduction. If your Auto Eat threshold is greater than or equal to the monster's max hit, you are safe to fight the monster afk as long as you don't run out of Food, ranged ammo or runes.
While all the information can be found in the game, this check can be difficult for dungeons, slayer tasks, and some late game monsters that have special attacks. Players have created tools to help check if you are safe to idle, but please note that they are liable to become out of date and inaccurate.
For more information:
- The website Can I Idle Melvor is an easy to use resource to determine if you can idle safely. As of 12/15/22, the website says it is out of date but it is still valid for v1.1.1 with the exception of Elite and Master Slayer Tasks once the player has beaten Impending Darkness Event and purchased the Throne of the Herald Expansion. This website only has monsters from the base game.
- The Combat Simulator mod is suggested to determine whether or not a particular Monster or Dungeon can be safely fought with your particular setup
- There is a new mod "Will I die?", although note that as with the combat simulator this cannot be guaranteed to be 100% accurate. Therefore, you should always exercise caution when fighting something for the first time. To learn about modding, see the Mods section of this FAQ
