What is PS? PostScript File Format Explained

What is PS?

PS (PostScript) is a page description language and file format created by Adobe Systems and released in 1984. A PS file contains instructions that describe exactly how a page of text, vector graphics and images should be rendered, primarily for printing.

PostScript is also a complete, stack-based programming language, so a PS file is effectively a program executed by a PostScript interpreter, such as one built into a printer or software like Ghostscript. It pioneered device-independent printing and helped launch desktop publishing. PDF later evolved as a more constrained, document-focused successor.

History and Standardization

PostScript was created by Adobe, founded by John Warnock and Charles Geschke, and released in 1984. Its arrival, together with the Apple LaserWriter and page-layout software, is what set off the desktop publishing revolution: for the first time an ordinary computer and a laser printer could produce typeset-quality pages. PostScript was the common language that let the software describe a page and the printer render it faithfully.

The language went through several major revisions. Level 1 established the core imaging model; Level 2 added better color, compression, and memory management; and PostScript 3 extended color handling and performance for high-end printing. For years it was the lingua franca of the professional printing industry, built into imagesetters, high-end laser printers, and the entire prepress workflow.

PostScript's most important legacy is PDF, which Adobe derived from the same imaging model but redesigned to be a fixed, self-contained document format rather than a program to be executed. As PDF took over document exchange and printing, raw PostScript faded from everyday use, though it survives inside many printer pipelines and as the foundation of the imaging model that PDF still uses today.

How PostScript Works

PostScript is not a picture format in the usual sense; it is a page-description programming language. A .ps file is a text program written in a stack-based language, and when a printer or interpreter runs that program, the commands it contains draw the page. This is a fundamentally different idea from a bitmap or a fixed document: the file tells the device how to construct the page rather than storing the finished pixels.

The language is stack-based and uses postfix notation, so operands are pushed onto a stack and operators consume them. Drawing is done with graphics operators such as moveto to set a current point, lineto and curveto to build paths, and fill or stroke to paint them. Because the page is built from mathematical paths and font outlines, it is resolution independent: the same program prints crisply on a 300 dpi office printer or a high-resolution imagesetter.

PostScript treats text as graphics too. Fonts are described as outlines, historically Adobe's Type 1 fonts, and glyphs are placed and filled like any other shape, which is why PostScript output can render type with exact positioning and scaling. A single program can mix vector paths, embedded raster images, and text, all handled by the same interpreter.

Running a PostScript program requires a PostScript interpreter, whether built into a printer's hardware or provided in software such as Ghostscript. The interpreter executes the program top to bottom, maintaining graphics state like current color and transformation matrix, and produces the rasterized output. This programmatic nature makes PostScript powerful but also heavier and less predictable than a fixed format, since the same file can behave differently depending on the interpreter and available fonts.

PostScript Compared to PDF and EPS

The most important comparison is with PDF, PostScript's own successor. PDF keeps PostScript's imaging model but removes the general-purpose programmability, so a PDF is a fixed, self-contained document rather than a program that must be executed. That makes PDF far more reliable and portable: fonts and resources are embedded, pages can be accessed randomly, and the file renders the same everywhere. For virtually every task where people once used PostScript, PDF is now the better choice.

Against EPS, the relationship is one of scope. EPS is a restricted, single-figure slice of PostScript with a mandatory bounding box, meant to be embedded as an illustration inside a larger layout. Full PostScript describes complete multi-page print jobs. In short, EPS is PostScript packaged for reuse as a graphic, while a plain .ps file is typically a whole document ready to print.

PostScript's lasting relevance is now mostly behind the scenes. Many printer drivers still generate PostScript, and tools like Ghostscript interpret and convert it, so the language quietly powers a great deal of printing. For creating or exchanging documents directly, however, it has been almost entirely replaced by PDF, and encountering a raw .ps file today usually means converting it to PDF before doing anything else with it.

MKV Technical Specifications

PS vs Other Document Formats

PostScript is a printer-oriented page language, while PDF evolved from it for reliable on-screen document viewing.

Advantages & Disadvantages

Common Use Cases

PS is used mainly in professional printing and publishing workflows.