Logic gates are the building blocks of all digital electronics: tiny decision makers that take one or two binary inputs and produce a single binary output according to a fixed rule. An AND gate outputs one only when both inputs are one, an OR gate when at least one is one, and a NOT gate simply inverts its input. Combinations of these gates form adders, memory, processors and every other digital circuit. This simulator lets you toggle two inputs and choose a gate, watching the output update immediately, which makes the abstract truth tables concrete. It is ideal for students meeting digital logic for the first time, and for anyone who wants to check a gate’s behaviour before using it in a larger design.
Quick Answer: Toggle inputs A and B, choose a gate, and read the live output. The current input values and result are always shown together.
Free Online Tool
Logic Gate Simulator
Toggle A and B, pick a gate, and watch the output live.
How to Use the Logic Gate Simulator
- Click Toggle A to switch input A between zero and one, and do the same for input B.
- Choose the gate you want to test from the dropdown list.
- Read the output value, which updates live as inputs or the gate change.
- Try all four input combinations for a two input gate to build its truth table from observation.
- Use the NOT gate with a single input to see inversion, noting that the second input is ignored for NOT.
Key Features
- Six gates: AND, OR, NOT, XOR, NAND and NOR, covering the standard gate set.
- Live output that updates on every toggle or gate change, with no separate run step.
- Clear display of both input values alongside the output, so the rule is visible in each state.
- Full combination exploration: all four input pairs can be tested in seconds.
- Local, instant simulation with no setup and no downloads.
Best Practices and Tips
- Learn NAND and NOR last, since each is simply the inverted version of AND and OR respectively.
- Notice that XOR outputs one exactly when the inputs differ, which is why it is the core of binary addition.
- Build a truth table by hand from the simulator’s outputs, since writing the table yourself cements the rules far better than reading one.
- Remember that real gates also have timing and voltage behaviour, but for logic learning the binary rule is what matters.
Common Mistakes to Avoid
- Expecting NOT to use both inputs. NOT has one input by convention, and this simulator uses input A for it.
- Confusing OR with XOR. OR outputs one when both inputs are one, while XOR outputs zero in that case.
- Assuming NAND outputs zero whenever any input is zero. NAND outputs zero only when both inputs are one.
Frequently Asked Questions
What is a logic gate?
A logic gate is a circuit that implements a Boolean function: it takes binary inputs, each zero or one, and produces a binary output according to a fixed rule. Gates are combined into larger circuits that perform arithmetic, store data and make decisions, forming the basis of all digital computers.
How do AND, OR and NOT differ?
AND outputs one only when all its inputs are one. OR outputs one when at least one input is one. NOT outputs the opposite of its single input. These three are functionally complete, meaning every other gate and circuit can be built from them alone.
What are NAND and NOR used for?
NAND is AND followed by NOT, and NOR is OR followed by NOT. They are important because each one alone is also functionally complete, and because in real chip manufacturing NAND gates are particularly efficient to build, so many circuits are implemented primarily with NAND gates.
Why does XOR matter?
XOR outputs one exactly when its inputs differ, which is precisely the sum bit when adding two binary digits without a carry. That makes XOR the heart of binary adders, and it also appears in parity checks and simple encryption operations.