Buff

A buff (symbol: ) is a term that is used to describe the strengthening of something, either through updating a game or by releasing a sequel. Buffs are often done to improve the performance of a tower, by strengthening towers that are considered too weak. The opposite of a Buff is a "Nerf," which involves the weakening of something between sequel games and between each game update. By convention, a "buff" is a balance change in relation to improving player ease, rather than reflecting the positive strength of game mechanic "ally" (e.g. towers, heroes, perks) or game mechanic "enemy" (e.g. bloons, map formatting, map obstacles).

The use of buffs has been introduced since Bloons TD 5 Flash, in which its earlier versions did introduce several series of balance changes for various towers in that game. It was later introduced for all other games of the Bloons TD 5 generation, excluding most console and Steam versions where there has lacked new significant balance changes beyond their older counterparts outside of bug fixes, with exception of Bloons TD Battles Steam. Bloons TD 6 introduces a significant portion of balance changes throughout every single update, and has been a core part of the game for the sake of providing variety in gameplay. Bloons TD Battles Mobile and its Steam counterpart have both still receive balance changes but at a much slower pace.

Definition
By convention, a "buff" refers to balance changes that make it easier for players attempting to utilize a game mechanic to their advantage. It often increases "desirable" stats or decreases "undesirable" stats, or it could be an overall advantageous rework to a specific feature in the game.

Formatting
On Bloons Wiki, a "buff" is marked with a Green Bloon with a green plus sign, plus following text that describes the buff.

Simple example:
 * UpgradeName cost decreased ($550 --> $450)

Refer to the documentation for Template:Buff for further details.

BTD6

 * Necromancer: Unpopped Army and Prince of Darkness received a giant overhaul of buffs in Version 21.0 to both reduce RNG and to boost its damage potential, to give them much stronger cleanup roles in their respective roles in the game.
 * Spiked Balls damage per spike increased by +1 in Version 19.0, which made it much stronger in the mid-game and a bit more worthy in the late-game at combating Super Ceramics.
 * Combinations of various MOAB Mauler buffs and Striker Jones buffs have made them powerful enough that the Striker Jones + Mauler spam strategy was one of the most powerful combos when it was embraced by the BTD6 community starting from Version 19.0.
 * Sub Commander received a considerable buff in Version 18.0 that allowed it to grant double damage to all nearby Subs, with exception of First Strike Capability ability missiles, instead of just a flat +1 damage.
 * Quincy's base price was reduced from $755 on Hard to $585 on Hard in Version 10.0, making him able to be bought at the start of CHIMPS. This made him far more versatile for the early-game, transforming him into a practical early-game role. He since sees the most use on Expert Maps as a starting hero.
 * The Biggest One's damage was massively increased from 20 to 60 in Version 9.0, which made it much stronger at handling Super Ceramics and weaker MOABs.
 * Superstorm had its blimp blowback potential greatly increased in a buff in Version 23.0. Before 23.0, it could only blow back one ZOMG per super-tornado. Afterwards, it has enough pierce to blow back all five children of a BAD with one super-tornado.
 * Shrapnel Shot was reworked in Version 17.0 to spawn shrapnel far more often in exchange for a conical spray of shrapnel instead of a radial spray of shrapnel. Initially, it could only spawn shrapnel if the targeted bloon and its children were eliminated in one hit, but 17.0 changed it to spawn shrapnel whenever the sniper damages its target.
 * Maim MOAB with Shrapnel Shot was buffed to allow its shrapnel to stun MOAB-class bloons in Version 22.0. Alongside other previous buffs to Maim MOAB + Shrapnel Shot, including the shrapnel rework in Version 17.0 and the much greater shrapnel damage in Version 19.0 and lead damage in Version 21.0, the 4-2-0 crosspath has become a viable grouped stun option.
 * Cluster Bombs and Recursive Cluster have both been directly buffed by the Frag Bombs buff in Version 28.0 that allows explosions to pop Black Bloons. This in turn has caused both aforementioned upgrades to become significantly stronger against mid-game rushes, as giving black-popping essentially overcame their only weaknesses.

BTD5 Flash to BTD5 Mobile and similar mobile games

 * Absolute Zero ability can now slow down MOAB-class bloons, allowing a useful alternative or even combination to the Sabotage Supply Lines.
 * In the Mobile versions of the games, an unexpected exploit appears where certain projectiles could duplicate under the influence of Monkey Fort, making projectiles much stronger than before (most noticeable with Glaive Riccochet and Hydra Rocket Pods).
 * Dart Monkey Darts have a much larger hitbox in mobile which noticeably improves their overall defending capabilities (especially with Triple Darts which can easily pop 3 layers at a time thanks to this).
 * Bloon Impact and Flash Bomb stuns bloons for much longer, making both upgrades more reliable at defending large bloon rushes.
 * Bloon Traps not losing monetary trap value across rounds makes Bloon Traps a more viable option for farming cash, especially in rounds where significantly more bloons may appear (Round 40 and above in BTD5 Mobile, Rounds 15 and above in BMCM, or Rounds 13 and above in BTDBM). In that way, one can Bloon Trap Farm by farming in cash via Bloon Trap and continually multiply the number of active Bloon Traps to exponentially gain more cash.

BTD Battles Mobile game updates

 * Update 4.6's large series of buffs to the Heli Pilot made it significantly more useful and reliable against defending all types of bloons, thus making it more popular in non-club arenas. Most notably is the immense buff to the Razor Rotors upgrade, having its total cost to get up being slashed by a grand total of $650.
 * The Mortar Tower was not nearly used as much compared to BTD Battles Flash due to the smaller explosions it created. However in Update 4.1 the blast radius size was increased significantly, as well as the tower getting some pretty large price cuts to some of its upgrades (most notably The Big One and Artillery Battery), drastically improving its role as a support tower and allowing it to become one of the most used towers in the game as well as opening up a lot of viable loadouts that use the Mortar Tower (most notably Ninja Farm Mortar).
 * In Version 4.1, a large number of price buffs to the Ninja Monkey, particularly to the Double Shot upgrade, has made Ninja Monkey a lot more reliable for early-game grouped-popping power. This is particularly true when used against Grouped Blues and above. Despite Version 4.6 and Version 4.9 nerfing the price of both Double Shot and Bloonjitsu, overall, the Ninja has become a lot more reliable in the early-game.