Guitar Designer is an app to help luthiers with the design of guitar body shapes. It represents the outline of a guitar body by a smooth curve controlled by a set of "control points" whose positions determine the shape of the curve: the control points define a broken line called the "control polygon", with the guitar outline being a smoothed version of the polygon that passes through its endpoints. The shape of the curve can be refined by moving, adding and deleting control points by touching the diagram on the screen.

The body shape can be symmetric, as in a typical acoustic guitar design, or asymmetric as often found in solid-body electric guitars. The app will also display a soundhole if desired for acoustic guitar design, as well as a "boundary rectangle" to define the overall length and width of the body design.

A design can be saved in an app-specific XML format that can be later re-opened and refined. The XML file is just a text file that contains a human-readable specification of the control point sequence if the locations and weights are desired. A design can also be exported as a PDF file that can be viewed and printed with any PDF app, or as a DXF file that can be opened and edited with a CAD application.