How to Build a Spider Farm

Spider spawners are among the most common dungeon spawners. Spiders drop string (for bows, fishing rods, wool, scaffolding) and spider eyes (for fermented spider eyes used in brewing). A spawner-based spider farm is compact and reliable, though spiders have a unique challenge: they climb walls and are 2 blocks wide, requiring special design considerations.

Why build a spider farm?

• String for bows, crossbows, fishing rods, wool, and leads.
• Spider eyes for fermented spider eyes (brewing ingredient for Potions of Weakness, Slowness, and Harming).
• XP from killing spiders (5 XP each).
• Spider spawners are common and easy to find in dungeons.

Materials list

Item	Quantity	Notes
Building blocks	~200	Walls and funnel
Water buckets	4-6	Pushing spiders to the funnel
Signs	10+	Water flow stops
Hoppers	4-6	Collection
Chests	2+	Storage
Glass panes or iron bars	~20	Kill chamber viewing
Slabs	50+	Anti-climbing measures and spawn-proofing
Magma blocks or campfires (optional)	10+	AFK kill method

The spider challenge

Spiders present two unique design problems compared to other spawner farms:

1. Wall climbing. Spiders climb vertical surfaces. Standard drop-shaft designs do not work because spiders cling to walls instead of falling. You need to prevent wall climbing or use water flushing.
2. 2-block width. Spiders are 1.4 blocks wide and 0.9 blocks tall. They cannot fit through 1-block-wide gaps that zombies and skeletons walk through easily. Your funnel needs 2-block-wide channels minimum.

Step-by-step build instructions

Step 1: Find and secure the spawner

Spider spawners are found in dungeon rooms (cobblestone walls, mossy cobblestone floor). Light up the room with torches to stop spawning while you build. Do not break the spawner.

Step 2: Expand the spawner room

Clear out the dungeon room to create a 9x9x4 area centered on the spawner. The spawner spawns mobs in a 9x9x3 area around it (4 blocks horizontal, 1 block above and below). Making the room 9x9 gives maximum spawn coverage.

Step 3: Create the water flushing system

Place water source blocks along one wall of the spawner room. The water flows across the floor and pushes spiders toward the opposite wall. At the opposite wall, create a 2-block-wide gap in the floor leading to a drop channel. Place signs at the end of the water flow to stop the water from entering the channel.

Top-down view:

  WATER ~~~~~~~~~~~~~~~~>  [Gap]
  WATER ~~~~~~~~~~~~~~~~>  [Gap]    --> Drop channel
  WATER ~~~~~~~~~~~~~~~~>  [Gap]

       SPAWNER in center

Water flows from left to right.
Gap at right side leads to drop channel below.

Step 4: Build the anti-climbing drop shaft

The drop shaft must prevent spiders from climbing. Two methods work:

• Water column: Fill the drop shaft with flowing water. Spiders cannot climb in water. The water pushes them down to the kill zone.
• Overhang method: Place signs or open trapdoors on the walls of the shaft. Spiders treat these as climbable surfaces but fall through them. Alternatively, make the shaft wider than 2 blocks so spiders cannot bridge across the walls.

Step 5: Build the kill chamber

At the bottom of the drop shaft, create a 2x1 collection area. Spiders stack here. Place glass panes or iron bars as a barrier so you can see and hit the spiders without them attacking you. The gap between glass panes is small enough for your sword to reach through but too small for spiders to fit through.

Step 6: Add hoppers and chests

Place hoppers under the kill zone floor, feeding into chests. String and spider eyes drop from the spiders' death position, so the hoppers need to cover the collection area completely.

Step 7: Remove torches and activate

Remove all the torches you placed for safety. The spawner room needs to be dark (light level 0) for the spawner to produce spiders. The spawner activates when a player is within 16 blocks.

AFK spider farm variant

For fully AFK operation, replace the manual kill chamber with one of these:

• Magma blocks: Spiders take damage from standing on magma blocks. Place magma at the bottom of the drop shaft with hoppers underneath. Spiders die automatically, but you get no XP.
• Entity cramming: If 24+ spiders occupy the same block, they take cramming damage and die. This is slow but works without any redstone.
• Campfire kills: Place campfires under the collection area. Spiders take fire damage and die. Hoppers beneath the campfires collect items.

How it works

The spawner checks for a player within 16 blocks, darkness (light level below 7 at the spawner block), and space for the spider's hitbox (1.4 wide, 0.9 tall). It spawns 1-4 spiders every 10-40 seconds. Water pushes the spiders away from the spawner into the drop channel. Gravity (and anti-climbing measures) brings them to the kill zone. Player kills yield string, spider eyes, and XP.

Efficiency stats

• String per hour: 200-400
• Spider eyes per hour: 60-120
• XP per hour: ~2,500-4,000

Common mistakes

• Funnel too narrow. Spiders are wider than other mobs. A 1-block-wide funnel causes them to get stuck. Use 2-block-wide channels minimum.
• No anti-climbing. Without countermeasures, spiders climb the drop shaft walls and never reach the kill zone. Use water or trapdoors.
• Standing too far from spawner. The spawner deactivates when no player is within 16 blocks. Position your kill station within range.
• Light leaks. Even a small light leak near the spawner prevents activation. Check for torch remnants and seal the room completely.

Frequently asked questions

Can spiders fit through a 1-block gap?

Spiders are 1.4 blocks wide and 0.9 blocks tall. They cannot fit through a 1-block-wide gap but can fit through a 1-block-tall gap if the width allows. Design your kill chamber accordingly.

Do cave spider spawners work with this design?

Cave spiders are smaller (0.7 wide, 0.5 tall) and can fit through 1-block gaps. The design works but needs modifications for poison damage (cave spiders inflict Poison). Bring milk buckets or use a longer drop to kill them outright.

Maximizing spider farm output

Several upgrades can improve your spider farm's performance beyond the basic design:

• Dual water streams: Instead of one water source, use water sources on two opposite walls that alternate with redstone-powered dispensers. This flushing system pushes spiders more reliably than a single stream and prevents them from clinging to the dry wall.
• Looting III sword: String drops increase from 0-2 to 0-5 with Looting III. Spider eyes go from a base 33% drop chance to a higher chance with each Looting level. Over extended AFK sessions, Looting III roughly doubles your string and spider eye output.
• Multiple spawners: If you find two spider spawners within 16 blocks of a single AFK point, build funnels for both. Dungeons sometimes generate close together, and combining spawners doubles output with minimal extra building.
• Sweep attack (Java): In the kill chamber, spiders stack in a 2-block-wide space. A Sweeping Edge III sword hits multiple spiders per swing, dramatically increasing your kill speed and XP rate.

What to do with string and spider eyes

String has several valuable uses: crafting wool (4 string = 1 wool), making leads (4 string + 1 slimeball), fishing rods (3 sticks + 2 string), bows (3 sticks + 3 string), crossbows, and scaffolding (6 bamboo + 1 string). On servers with active economies, string and wool are always in demand for building projects. Spider eyes craft into fermented spider eyes (spider eye + sugar + brown mushroom), which are required ingredients for Potions of Weakness, Potions of Slowness, and Potions of Harming. If you run a potion brewing operation or a villager curing setup (which needs Weakness potions), a spider farm feeds directly into your potion supply chain.

Need a server that handles all this? Astroworld Hosting, NVMe SSDs, Pterodactyl panel, DDoS protection on every plan.