Bloons TD 6 (Bloons Tower Defense 6 in full[3] and often abbreviated as BTD6) is the sixth numbered installment in the Bloons TD series. It is the sequel to Bloons TD 5 and introduces new mechanics such as Heroes, Monkey Knowledge, and Paragons. It is the first Bloons TD game to utilize 3D graphics (the first Bloons game in general to have fully 3D graphics is the mobile version of Bloons Supermonkey 2) and the first to not have a web browser version. It follows the same gameplay conventions established in Bloons TD 5, but introduces new mechanics such as Heroes, tier 5 upgrades, three upgrade paths, and line of sight.

The original version of Bloons TD 6 was released on iOS and Android first, then ported to PCs with minor differences. It is the basis of Bloons TD 6+, Bloons TD 6 NETFLIX, the console version, and the Chinese version, which have more substantial differences. The game is also the basis of Bloons Adventure Time TD and Bloons TD Battles 2, which have similar game mechanics; they are sometimes unofficially referred to as the "Bloons TD 6 generation" collectively. 

New tracks tagged #MonkeyStep