Safes can be found within Gielinor and depending on their location, require different levels to be opened. There are currently 49 different safes, a list of which can be found here. To effectively open safes, players are required to go to the Safe-cracking trainer in the Thieves' Guild.
A loot bag is needed to open safes, and it is highly recommended to have a stethoscope as this increases the success rate of cracking safes.
A safe can have between 3-6 locks which need cracking; this can be done by clicking once and leaving, or click the safe every time it gains a blue highlight (there is also a different sound effect when this happens so it is advised to have sound effects on).
After successfully cracking the safe, you will add to your loot bag, and there is a chance to receive a special item and/or a clue scroll.
Cracking safes and fencing your loot bag at the Thieves' Guild rewards players with thieving experience, gold pieces and pilfer points.