Effect

An effect is a helpful or harmful condition that affects an entity. Effects can be inflicted in various ways throughout the game, including consuming potions and some food items, being in the range of beacons and conduits, and being attacked by or close to certain mobs.

The command allows players to inflict effects upon themselves and other entities.

Behavior
Any entities inflicted by an effect are affected in various ways for an amount of time. During the effect, spiral-shaped particles emanate from the position of the inflicted entity. For most effects, higher levels increase the strength of the effect.

In, players can open their inventory to see any current effects afflicted upon them, as well as its level and duration. In, effects are displayed in a separate screen, which can be opened by pressing on a keyboard, pressing // on a controller, or tapping the effect icon when using touch controls.

Internally, in the command, and in potion Amplifier NBT tags, the game stores an "amplifier" value, which is one less than the displayed level. For example, Strength II has an amplifier value of 1.

Due to the way this amplifier is stored in NBT, amplifiers of 128 to 255 (levels 129 to 256) in NBT tags (e.g. on potions) are treated as if they were −128 to −1 (levels −127 to 0) respectively. The command initially applies such amplifiers in their positive-valued sense but this is later converted to the negative-valued interpretation, leading to inconsistent results. In, amplifiers above 127 translate to positive levels, like other amplifiers.

Any number of different effects, including opposing effects such as Strength and Weakness, can be simultaneously active on a player. However, it is not possible to apply the same effect multiple times, even if they are of different levels (e.g. Strength and Strength II). When applying an effect already active on the player, higher levels overwrite lower levels, and higher durations overwrite lower durations of the same level.

In, when the stronger effect then overrides the weaker effect, the weaker effect remains, but is hidden. It returns after the stronger effect expires, if the weaker effect has a higher duration than the stronger effect. This change makes it impossible to create custom potion antidotes by applying an amplified effect with a one tick duration.

Every time when you leave the game with the status effects that have a level of 255, they become lower and weak when you come back into your world. The way to make status effects stay with the same level every time you go back into the game is that you need the level to be 100 in order to succeed.

In, when a stronger effect overrides the weaker effect, the weaker effect is deleted and does not return.

Note that even with commands, effects cannot be made to last forever. If an effect duration is set greater than 32766 (215−2) ticks, 27 minutes and 18 seconds, or 1638 seconds, it displays as "**:**", but still continues ticking down and eventually expires.

All effects can be removed by drinking milk, dying, being saved from death by a totem of undying, or traveling through the return portal in the End. Single-player users with cheats enabled and operators in multiplayer servers can use or  to achieve the same goal.

Damage dealt by effects (a kind of "magical damage") completely bypasses armor, making it a good way to deal with highly-armored targets (Protection enchantments reduce damage taken from effects in only). Witches are the only mob to have natural protection against effects, taking 85% less or 95% less damage from effects, except Wither.

Effect list
Positive effects have blue text in potion information, and in are displayed on the upper row of effects in the heads up display, while negative effects have red potion text and are displayed in the bottom row. Neutral effects have the blue potion text and are listed with the negative effects in the bottom row in the heads up display.

Trivia

 * When having multiple effects, the effects' timers are reduced by 1 second each simultaneously, regardless of when the player took each potion. This is because they use the same "seconds counter" that "ticks" every 20 game ticks to save memory. For example, if the player drinks one potion and another different potion that doesn't reset the timer 5.5 (or any non-integer amounts) seconds later, both effects' timers subtract 1 second from both of them simultaneously.
 * When a creeper has an effect and explodes, it leaves an area effect cloud for each effect that it had before it died.
 * Using a potion of Leaping II, a potion of Slow Falling, and a potion of Swiftness II, the player can jump a 9 block gap.