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Optional Local Setup: Icarus Verilog and GTKWave

How to install Icarus Verilog and GTKWave locally, and the compile/run/view workflow behind every example in this tutorial — useful once you want a project outside the browser.

4 min read · Updated

You do not need a local install to follow this tutorial or the free course — every runnable example here compiles and simulates server-side in the playground. A local toolchain becomes useful once you want to work offline, script a build, or keep a project in your own repository.

This tutorial's own examples are compiled and simulated with Icarus Verilog, an open-source simulator. GTKWave is a companion waveform viewer for the VCD files Icarus can produce.

Installing Icarus Verilog

Platform Typical install
Debian/Ubuntu Linux sudo apt-get install iverilog — this is exactly what this tutorial's own CI pipeline runs to compile the verified examples on this page's siblings, so it's confirmed working, not just documented
macOS (Homebrew) brew install icarus-verilog. The Bison requirement applies when building Icarus from source with Xcode, not to the normal Homebrew-install command; if you take that source-build path, Icarus's guide says to install Bison 3 and put it on your PATH
Windows The project's own install guide currently recommends MSYS2, which carries prebuilt Icarus Verilog and GTKWave packages together. A native installer from bleyer.org or scoop install iverilog also work, though the Scoop package can lag behind the latest release

Confirm the install from a terminal:

iverilog -V

That should print a version banner, for example Icarus Verilog version 12.0 (...). If the command is not found, the install did not add iverilog to your shell's PATH.

The compile/run/view workflow

Icarus Verilog is two programs used together: iverilog compiles, vvp runs the compiled result.

iverilog -o sim.vvp design.v testbench.v
vvp sim.vvp

design.v is the synthesizable module under test; testbench.v supplies stimulus and typically ends in $finish. If the testbench calls $dumpfile/$dumpvars, running sim.vvp also writes a .vcd waveform file in the current directory — see Reading Waveforms for how to interpret one.

Installing GTKWave

Platform Typical install
Debian/Ubuntu Linux sudo apt-get install gtkwave
macOS Do not rely on GTKWave's older packaged macOS build: its official documentation says it is incompatible with current macOS. Follow the current GTKWave macOS instructions: use its linked community Homebrew tap or build GTKWave 4 from source
Windows Bundled with the MSYS2 or bleyer.org Icarus installs above, or a standalone installer from the GTKWave project page

Open a generated waveform with:

gtkwave wave.vcd

GTKWave opens with no signals shown by default — drag the modules and signals you want from the left-hand hierarchy pane into the waveform view.

Common setup mistakes

  • Compiling without the testbench file. iverilog -o sim.vvp design.v alone has no stimulus and nothing to simulate; both files belong in one iverilog invocation unless you compile them to separate object files first.
  • No $dumpfile/$dumpvars in the testbench. Without both system tasks, vvp runs correctly but produces no .vcd file for GTKWave to open.
  • Two modules named tb colliding when you concatenate files from different examples — Icarus reports a duplicate-module error, not a silent overwrite.
  • An outdated Bison while building Icarus from source on macOS. The normal brew install icarus-verilog path is separate. If you are following Icarus's source-build instructions with Xcode, install Bison 3 and put it on PATH as the official macOS guidance describes.

Where to go from here

Nothing on this page changes anything else in the tutorial: it exists for readers who want the same toolchain running on their own machine. What Is Verilog HDL? covers what a simulator and a synthesis tool each do; Where Verilog Fits in the Toolchain places Icarus among the broader set of tools you will encounter.

Sources and verification

  • Icarus Verilog — official installation guide — Homebrew formula name, the source-build-only macOS Bison caveat, and the current Windows recommendation (MSYS2) all confirmed here, 2026-08.
  • GTKWave — macOS install guide
  • This tutorial's own CI installs Icarus via apt-get install iverilog on Ubuntu runners (.github/workflows/ci.yml) to compile every verified example in this tutorial, which is a second, independent confirmation of the Linux command beyond the official docs.