Safe

Type	FurnitureStorage
Placeable	✔️ (2 wide × 2 high)
Use time	15 (Very fast)
Tooltip	Can be used to store your items; Stored items can only be accessed by you
Rarity
Buy	20 GC
Sell	4 GC
Research	1 required

The Safe is a portable storage item with 40 slots to store other items. The Safe, Piggy Bank, Defender's Forge(Desktop, Console and Mobile versions), and Void Vault have the unique ability to be carried while they contain items. It is purchased from the Merchant for 20 GC each, after Skeletron has been defeated.

The Safe functions identically to the Piggy Bank, besides it can be placed on platform or furniture surface, it can also be placed on Blocks.

Differences from Chests

The Safe (as well as the Piggy Bank, Defender's Forge, and Void Vault) functions similarly to other storage items, but with some important differences:

Each Safe contains the same items (when accessed by the same character), no matter where they are placed within a world.
Purchasing multiple Safes will provide more points of access to its storage, but will not expand its capacity whatsoever.
The Safe can be picked up even when it contains items. This makes it a viable way to expand a character's inventory slots. It must be placed in order to add or remove items, and can be freed again with any Pickaxe.
The Safe's contents are saved with character data, instead of the world data. Its contents are kept from world to world, and from server to server.
The Safe's contents are exclusive to each player, so any characters' stored items will not be accessible to others unless they are removed from storage first, and vice versa. This makes it useful for item security on PvP servers where stealing is allowed.
Multiple players can use the same Safe without having access to each others items. Each player will only see their own items when accessing the same Safes.

Notes

Coins stored in a Safe, Piggy Bank, Defender's Forge, or the Void Vault will not be lost in case of death, even if said container itself is within the character's inventory at their time of death.
The Safe was likely added because many players complained about running out of inventory space while looting the Dungeon. This might also explain why it is purchasable only after defeating Skeletron.
Money stored in the Piggy Bank, the Safe, the Defender's Forge, and the Void Vault are added together and are available when purchasing things from NPCs. The total money stored is visible as Savings to the right of a NPC shop window.