How to Make an Observer in Minecraft

Guide Java Bedrock

Quick answer: Craft an observer with 6 cobblestone, 2 redstone dust and 1 nether quartz. Its face watches the block in front and the red dot side fires a redstone pulse whenever that block changes - the heart of every automatic farm.

What you need

Cobblestone x6
Redstone dust x2
Nether quartz x1
Crafting table

Step by step

Gather 6 cobblestone, 2 redstone dust and 1 nether quartz (mine quartz ore in the Nether).
Craft the observer: cobblestone filling the top and bottom rows, redstone dust in the middle-left and middle-center, nether quartz in the middle-right.
Aim it: the face with the eyes points away from you when placed, watching the block in front; the red dot (output) faces toward you.
Detect changes: whenever the watched block updates - crops growing, water flowing, a furnace finishing, a chest opening - the observer emits a pulse.
Use the pulse: in Java it is a strong 15-strength pulse lasting 2 game ticks (1 redstone tick); in Bedrock it aligns to redstone ticks. Wire the dot side to pistons, lamps or note blocks.
Build a clock: place two observers facing each other - each detects the other's pulse and they fire forever until broken. This observer clock runs most farms.
Chain flying machines: observers also pulse when a piston moves them, which is what makes self-propelling flying machines possible.
Hide a trap: an observer watching a chest or door fires when a player uses it - the classic alarm and trap trigger.

Java vs Bedrock

Recipe and detection work the same in Java and Bedrock, but pulse timing differs: Java emits a 2-game-tick (1 redstone tick) pulse, while Bedrock aligns to redstone ticks and detects updates only on odd game ticks. Timing-sensitive contraptions often behave differently between editions.

Versions: Added in Java 1.11 (16w39a), arriving in Bedrock with 0.15.0 - Bedrock actually got observers first. Since then it has become the most-used block in redstone farming.

Frequently asked questions

How does an observer work in Minecraft?

The face side watches the single block directly in front of it. When that block's state changes in almost any way, the red dot side emits one short redstone pulse. Crops growing a stage, water appearing, a piston extending or a chest opening all trigger it.

Why is my observer clock not working?

The two observers must face each other - eye side to eye side. If a contraption works in one edition but not the other, it is usually the pulse timing: Java pulses last 1 redstone tick and Bedrock aligns them to its own tick schedule.

What is an observer used for in Minecraft?

Automatic farms (sugar cane, bamboo, pumpkins), flying machines, hidden doors, traps, item counters and compact clocks. Almost every redstone build past beginner level includes at least one.