Spider

Spiders are common neutral mobs that have the unique ability to climb walls.

Spawning
1-4 spiders spawn in a 3×3×1.5 space on opaque blocks in the Overworld at a light level of 7 or less. The top blocks can be transparent, but not solid.

A spider spawns in leaves provided that there are 3×3×2 spaces around as forested biomes have a greater amount of spiders; they do not spawn in groups.



Spawners
Spiders spawn from spawners in dungeons (25% chance), as well as secret rooms surrounded by cobwebs in woodland mansions.

Status effects
On hard difficulty, spiders occasionally spawn with status effects. For each pack spawn, there is a (10&times;clamped regional difficulty)% chance of the game applying a status effect. This does not apply to cave spiders. If it decides to do so, then it selects the effect. The spider can spawn with following effects: The effect is then applied to all entities within the pack with an endless length. If the Invisibility status effect is applied to a spider, its eyes remain visible.
 * (40% chance)
 * (20% chance)
 * (20% chance)
 * (20% chance)

Drops
Upon death, a spider drops:
 * 0–2 . The maximum is increased by 1 per level of Looting, for 0-5 string with Looting III.
 * when killed by a player or tamed wolf.
 * A $1/3$ chance of dropping a spider eye when killed by a player or tamed wolf. The maximum amount of spider eyes is increased by 1 per level of Looting. The chance of a spider not dropping any spider eyes can be found using the formula . For example, Looting III gives a $1/3$ chance of not dropping any spider eyes. All other amounts have an equal chance of occurring.

Behavior
Spiders are hostile to players and iron golems as long as the light level immediately around them is 11 or less; otherwise, they do not attack unless attacked. Hostile spiders see up to 16 blocks, continuing to chase even when exposed to well-lit locations. If a spider sustains damage from a source other than a direct attack, such as falling, its hostility resets to a neutral state.

Spiders can climb up over solid blocks but not overhangs or on ceilings. If a spider cannot find an ideal path to the player, when they go behind or on top of a wall, it approaches as close as it can to the player's position from the outside or below as it can see through blocks, at that time proceed by climbing the wall vertically until it gets to the top, even if it loses its aggression toward them. When a spider loses its aggression, it continues moving forward blindly for 2 seconds; this behavior causes the spider to climb up any walls in its path.

Spiders cannot climb magma blocks. Note that Cave Spiders, on the other hand, can climb them on all editions.

If a spider tries to go through the world border, it starts climbing the world border instead.

If shot with arrows whereas outside of the detection range, spiders turn and run in the direction from which the arrow was fired. If the player moves away, the spider continues following the same path unless the player enters the detection range, in which case the spider changes direction and attacks.

Even though spiders do not inflict the Poison status effect, they are immune to it. They are also immune to the slowing applied to most mobs when walking through cobwebs.

An aggressive spider pounces at close range. Whether it is swimming in 1-block-deep water, it pounces upon touching the submerged floor. They can attack when their Y-axis position is changed.

Spiders flip onto their backs when they die, unlike all other mobs, which land on their sides.

They were the first arthropod to be added to the game. The Bane of Arthropods enchantment inflict Slowness IV and more damage to spiders.

Spiders in Minecraft Dungeons have different behavior than spiders in normal Minecraft. Instead of attacking by biting the player, they throw webs at the player to trap them, and then they rush to the player to bite them. They are also always hostile.
 * Minecraft Dungeons

Spider jockeys
There is a 1% chance for a spider to spawn with a skeleton riding it, forming a spider jockey. In the Nether, a spider spawned there with a spawn egg, commands or spawners, has a 0.8% chance to spawn a wither skeleton on its back and form a wither jockey instead. In some of snowy biomes, a spider has a 0.8% chance to spawn a stray on its back and form a stray jockey instead. A spider jockey can also be spawned by the command.



Data values
Spiders have entity data associated with them that contain various properties of the mob.

Video
Note:This video says that cave spiders can poison you but not in easy difficulty.