Ghostscript is a free software interpreter for the PostScript page-description language and, later, for PDF. It does the same essential job a PostScript laser printer does, rasterizing the drawing instructions in a document into actual pixels, but it does it in software on a general-purpose computer. That means a machine without an expensive PostScript printer can still view PostScript files on screen, print them to an ordinary non-PostScript printer, or convert them into other formats. Ghostscript was started by L. Peter Deutsch, a veteran of Xerox PARC, and first released in the late 1980s.
The interpreter matters because PostScript, when Adobe introduced it, was expensive. A printer needed a built-in PostScript interpreter licensed from Adobe, which added significant cost and shut out cheaper hardware. Ghostscript broke that dependency by providing a free, independent implementation of the language. A user could send PostScript output from any application to Ghostscript and have it rendered to whatever device they actually owned, or to a raster image, or to PDF. This made the PostScript imaging model available far beyond the world of dedicated PostScript printers.
Over time Ghostscript grew well past its original role. The project’s documentation describes a wide range of output devices and formats, including the ability to read PDF as well as PostScript and to convert freely between them, making Ghostscript a general-purpose engine for both of Adobe’s formats. It became the rendering core behind many printing systems, document viewers, and file-conversion utilities, often invisibly, as the component that turns PostScript or PDF into the dots a printer or screen needs.
Ghostscript has a notable licensing history that mirrors the broader free-software story. Deutsch released versions under the GNU General Public License through the GNU Project while also distributing a separately licensed Aladdin edition through his company Aladdin Enterprises, an early example of the dual-licensing model in which the same code is offered under both a free license and a commercial one. The software is today maintained by Artifex Software together with the wider user community, with current releases continuing under open-source and commercial terms.
As a tool, Ghostscript occupies a key place in the practical history of desktop publishing and document handling. It democratized access to Adobe’s page-description technology, underpinned countless open-source printing pipelines, and remains a standard building block whenever PostScript or PDF must be displayed, printed, or transformed on systems that do not natively understand those formats.