OR GATE
Outputs ON when ANY input is ON. The simplest multi-input gate, just merge two redstone dust lines into one. No torches needed for basic OR functionality.
Truth Table
| Input A | Input B | Output |
|---|---|---|
| 0 (OFF) | 0 (OFF) | 0 (OFF) |
| 0 (OFF) | 1 (ON) | 1 (ON) |
| 1 (ON) | 0 (OFF) | 1 (ON) |
| 1 (ON) | 1 (ON) | 1 (ON) |
Overview: what the OR Gate is and does
Outputs ON when ANY input is ON. The simplest multi-input gate, just merge two redstone dust lines into one. No torches needed for basic OR functionality.
In plain terms, the output is on whenever at least one input is on. OR is the most natural gate in redstone because two dust lines that simply meet already behave as one — it is how you let any of several triggers fire the same mechanism.
This page describes the gate as it behaves in Java Edition 1.21; the truth table and timings below match vanilla redstone exactly.
How it works: the redstone mechanics
Across its four input combinations the output is on in 3 cases — A off with B on, A on with B off, and A on with B on — and off in the remaining 1.
Expressed as boolean algebra that is output = A OR B.
A bare dust-merge OR adds no delay at all; only the optional isolating repeaters on each input cost ticks.
Because redstone signals are just on or off, "on" here means a powered line (signal 1-15) and "off" means an unpowered line (signal 0); the gate cares only about presence or absence of power, not its exact strength.
How to build it
- 1Run input A as redstone dust toward the output point.
- 2Run input B as redstone dust toward the same output point.
- 3Where the two dust lines meet, they naturally combine into an OR gate.
- 4If either input has signal, the output will be powered.
- 5For isolation, use repeaters on each input before merging.
- 6Verify it against the truth table: setting the inputs to OFF and ON should drive the output ON. Walk through every input combination once to confirm the gate matches the table above.
Uses & applications
- ▸OR is the most natural gate in redstone because two dust lines that simply meet already behave as one — it is how you let any of several triggers fire the same mechanism.
- ▸Direct dust merge (simplest, just join two lines) — a practical build choice for this gate.
- ▸Repeater-isolated OR (prevents signal backflow) — a practical build choice for this gate.
- ▸Multi-input OR (just add more lines to the merge point) — a practical build choice for this gate.
Tips & common mistakes
- !Keep your inputs isolated with repeaters if signals are flowing back into each other; uncontrolled backflow between dust lines is the most common reason a gate reads the wrong value.
- !Remember the propagation cost: A bare dust-merge OR adds no delay at all; only the optional isolating repeaters on each input cost ticks. If you chain several gates, those ticks add up and can desynchronise a fast circuit.
- !When a multi-gate circuit misbehaves, test each gate in isolation against its own truth table before assuming the wiring between them is at fault.
OR Gate FAQ
What does an OR Gate do in Minecraft?
A OR Gate outputs a signal where the output is on whenever at least one input is on. In boolean terms, output = A OR B.
What is the truth table of an OR Gate?
Across its four input combinations the output is on in 3 cases — A off with B on, A on with B off, and A on with B on — and off in the remaining 1. The boolean expression is output = A OR B.
How do you build an OR Gate with redstone?
Run input A as redstone dust toward the output point. Run input B as redstone dust toward the same output point. Common variants include direct dust merge (simplest, just join two lines) and repeater-isolated OR (prevents signal backflow).
How much delay does an OR Gate add?
A bare dust-merge OR adds no delay at all; only the optional isolating repeaters on each input cost ticks. That matters most in clocks and adders where every redstone tick counts.