Gwave is a waveform viewer. Its purpose is for viewing analog data, such as the output from Spice-like simulations. Gwave can read binary or ascii files written by HSpice from transient, AC, or Sweep analyses, "raw" files written by Spice2, Spice3, or ngspice, and transient analysis files from the CAzM simulator. It can also read a generic tabular ASCII format suitable for use with ACS or homegrown tools. It supports multiple "panels" (graticlules) with multiple variables displayed in each. Two vertical-bar cursors are available for time-difference measurements. Multiple files can be loaded, for comparing the results of several simulations. Much of Gwave's user interface is written in the Guile extension language and is therefore easily extensible for custom applications without recompilation.