GTKWave

GTKWave is a free, open-source waveform viewer for digital logic simulations. It presents time-ordered signal traces from dump files produced by digital simulators such as Verilog, VHDL, and SystemVerilog. Designed to handle large waveforms efficiently, GTKWave focuses on fast navigation and flexible signal organization rather than editing or simulation itself.

GTKWave reads a variety of trace formats, most notably VCD (Value Change Dump) and the LXT2 format, and supports additional formats through parsing plugins or conversion. Users can add signals to the waveform window using hierarchical names, group signals into buses, and color-code traces. The viewer provides features such as time cursors, zooming, markers, search-based signal selection, and project files (.gtkw) to preserve the layout of a waveform session.

The user interface is built on the GTK+ toolkit, which makes GTKWave portable across platforms. It runs on Linux, Windows, and macOS, and can be built from source or installed via distribution packages.

GTKWave is developed and distributed under the GNU General Public License. It is maintained by a community of contributors and is widely used in open-source hardware verification workflows, including those involving Verilog, VHDL, and mixed-language simulations.

Typical workflows involve generating a VCD or other supported dump from a simulator, opening the file in GTKWave, selecting signals of interest, organizing them into groups, and saving the session for later review.