Verilog Online Compiler

Verilog is a hardware description language (HDL). Unlike software languages that describe what a program does, Verilog describes what a circuit looks like. You define modules with inputs and outputs, wire them together, and simulate how signals propagate. It's the standard language for FPGA programming and digital IC design.

The catch with Verilog is that professional simulation tools -- ModelSim, Vivado, Quartus -- are large and often require licenses. If you just want to check whether your logic for a simple module is correct, that's a lot of overhead.

Simulating Verilog online

A Verilog online compiler (technically a simulator) lets you write a module and its testbench, then run the simulation to see waveform output or printed results. No EDA tool installation, no license server. Useful for:

Students learning digital design concepts
Quick verification of combinational or sequential logic
Sharing a circuit design with someone for review

A simple 4-bit counter module

module counter(
    input clk,
    input reset,
    output reg [3:0] count
);
    always @(posedge clk or posedge reset) begin
        if (reset)
            count <= 4'b0000;
        else
            count <= count + 1;
    end
endmodule

// Testbench
module tb;
    reg clk, reset;
    wire [3:0] count;

    counter uut(.clk(clk), .reset(reset), .count(count));

    initial begin
        clk = 0;
        forever #5 clk = ~clk;
    end

    initial begin
        reset = 1;
        #12 reset = 0;
        #160 $finish;
    end

    initial begin
        $monitor("Time=%0t reset=%b count=%b (%0d)",
                 $time, reset, count, count);
    end
endmodule

This defines a 4-bit counter that increments on every rising clock edge and resets to zero when the reset signal is high. The testbench drives the clock and reset signals, and $monitor prints the counter value at each change. This is a typical pattern in Verilog simulation -- you write the design module, then write a testbench to exercise it.

OneCompiler for Verilog simulation

OneCompiler runs Verilog simulations and displays the text output from $display and $monitor calls. It handles standard Verilog constructs, so you can test modules, write testbenches, and verify logic without touching a full EDA suite.

Simulate your Verilog here: Verilog Online Compiler on OneCompiler