Garbage

Garbage is a form of "attack" in multiplayer Tetris that has been around since Tetris (Game Boy). Sending garbage is done by clearing multiple lines, which causes rows with holes to appear at the bottom of your opponent's playfield. Games with color graphics typically show garbage rows in gray as opposed to the rest of the playfield having colored blocks

Garbage System

In most instances, when a player makes certain line clear types, a corresponding amount of garbage lines is then sent to an opponent's receiving queue. The incoming amount of garbage lines is then added to the bottom of an opponent's playfield on the latter's next piece drop or non-line-clear. An opponent can also counter-attack by performing line clears to reduce or eliminate the incoming garbage in the receiving queue; any leftover counter-attack amount is then sent back as garbage lines to the first player.

Garbage lines can appear as broken rows with holes, solid rows, etc. For games with broken-line garbage, the random rate of the hole(s)' alignment varies per game.

General Garbage System in Guideline Games:

Clear Type	Rows Cleared	Garbage Rows Sent
Single	1	0
Double	2	1
Triple	3	2
Tetris	4	4
Mini T-Spin Single (wherever available)	1	0
Mini T-Spin Double (wherever available)	2	1
T-Spin Single	1	2
T-Spin Double	2	4
T-Spin Triple	3	6
Back-to-Back Bonus	0	+1 (MTSS, MTSD; TSS), +2 (TSD; Tetris); +3 (TST)
Perfect clear	1-4	10 (+ last line clear type if applicable)

Several Guideline-based Tetris games can also reward additional garbage rows when making combos.

For games with multiplayer modes that support more than 2 players, the player cycles through each of the opponents for sending garbage to (known as targeting), which is done either with a fixed-time distribution cycle method or through manual / pre-set targeting options.

Some games will deviate from this. For example, sending more than one gap per row (Tetris The Grand Master Ace) or having 1:1 clear to send ratio (Super Tetris 3).

Games with random garbage, like Tetris Worlds, will mathematically output two aligned garbage holes (an easy double) 1:10 garbage lines, three aligned every 1:100, and four aligned every 1:1000.

Some games, like Tetris DS feature semi-random garbage output. With random garbage, the player will receive at least a double's worth of aligned holes 10% of the time. Empirical data suggests Tetris DS leans closer to 72%.

Early games like Tetris (Game Boy) will switch the garbage's hole column every nine rows or so.

Some players prefer pure random garbage because aligned garbage tends to "see-saw" back and forth wildly. Others enjoy the depth and challenge presented by random garbage.

Tetris Worlds is currently the only game which lacks retaliation garbage, meaning clears from garbage will not send back any garbage. Because of this, clearing garbage becomes less desirable, which a player may argue deprives the game of some depth.