Free Online Logic Gate Simulator — Build Digital Circuits in Your Browser
The EcrioniX Logic Gate Simulator is a free, browser-based digital circuit simulator — a modern, no-install alternative to Logisim that needs no Java and no signup. Drag logic gates onto the canvas, wire them together, toggle the inputs, and watch the signals propagate in real time on any laptop, tablet or phone.
What you can build
- Universal gates — AND, OR, NOT, NAND, NOR, XOR, XNOR with live colour-coded wires.
- Combinational circuits — half adder, full adder, and a 4-bit adder as ready-made blocks (or build them from XOR/AND/OR).
- Sequential logic — D flip-flops, an SR latch, and ripple counters driven by a clock.
- Displays — wire bits to a 7-segment, a 4-to-7 decoder, or the Hex/Signed display. Unsigned shows 0–F; signed uses 4-bit two's complement (−8…+7) with a minus bar.
- Auto clock — a 1 Hz–10 Hz clock source so circuits run on their own.
- Waveform probe — attach a probe to any node for an oscilloscope-style trace.
How to use it
- Click a gate in the palette, then click the canvas to place it.
- Click a green output dot, then a blue input dot, to draw a wire.
- Click an input switch to toggle it; HIGH wires light up green.
- Right-click a component or wire to delete it; drag the body to move it.
- Use the built-in templates or the Truth Table → Circuit generator to start fast.
- Configurable ports: select a gate, MUX, DEMUX or RAM, then press [ or ] to change its port count — gate inputs (2–8), MUX/DEMUX size (2:1 → 8:1), or RAM depth (2–8 words). Select the Hex/Signed display and press [ / ] (or double-click) to switch unsigned ↔ signed.
Adders and signed numbers
Drop a Half Adder (S = A⊕B, Cout = A·B), a Full Adder (A+B+Cin), or a 4-bit Adder (ripple of four full adders: A[3:0] + B[3:0] + Cin). Wire S0–S3 to the Hex / Signed block. The adder also prints unsigned and signed values on its face so you can see that 1111 is 15 unsigned and −1 in two's complement. Overflow of signed add is not the same as Cout — see Two's Complement.
Why a browser logic simulator?
Classroom tools like Logisim are powerful but need installation and Java, and won't run on a phone. A browser simulator loads instantly, works on any device, and lets you share a circuit by saving the .ecx file. It's ideal for ECE and EEE students learning Boolean algebra, for checking a gate-level idea quickly, or for revising flip-flops and counters before an exam or interview.
Frequently asked questions
Is the logic gate simulator free?
Yes — completely free, runs in your browser, no install, signup or Java. Save your work as an .ecx file and reopen it anytime.
Is this a Logisim alternative?
Yes. It offers the same drag-and-drop gate placement, wiring and live simulation as Logisim, plus a waveform probe, auto clock, 7-segment display and a truth-table-to-circuit generator — with nothing to download.
Can I simulate flip-flops and counters?
Yes. Place a D flip-flop, drive it with the clock source, and build registers or a ripple counter; the waveform probe shows the timing.
Can I build multiplexers, demultiplexers and RAM?
Yes. Place a MUX 4:1, DEMUX 1:4 or RAM 4×1 from the Data Routing palette. Their port counts are configurable — select the block and press [ or ] to scale a MUX/DEMUX from 2:1 up to 8:1, or grow the RAM from 2 to 8 words. The RAM writes on a clock edge when WE=1 and reads asynchronously.
Can I show negative numbers on the 7-segment?
Yes. Place Hex / Signed and wire D0–D3 (LSB first). Unsigned mode shows 0–F. Double-click (or press [ / ]) for signed two's complement: a red minus bar plus the absolute digit for −8…+7.
How do I wire a 4-bit adder to the display?
Use the 4-bit Adder + 7-seg template, or place a 4-bit adder and connect S0→D0, S1→D1, S2→D2, S3→D3. Cout is a separate LED. You can also send S[3:0] through the 4→7 decoder into a raw 7-segment.
What else can I try?
Play the Logic Forge puzzle game, design state machines in the FSM Designer, or read two's complement and the Digital Electronics guides.
Related: Logic Forge Game · FSM Designer · Two's Complement · Digital Electronics