What is PFB? The PostScript Type 1 Binary Font Format Explained

How PFB Works

PFB stands for Printer Font Binary, and it is the file that holds the glyph outlines of an Adobe PostScript Type 1 font. A Type 1 font describes each letter with cubic Bezier curves, the same mathematics used to draw smooth outlines in illustration software, and pairs those outlines with a small program that hints how they should be rendered at small sizes. The PFB file is the binary packaging of that outline data and its associated code.

A distinctive quirk of Type 1 is that most of the interesting content is encrypted. Adobe protected the charstrings that define each glyph and the private hinting data with a simple, published encryption scheme called eexec. The purpose was less to lock users out than to discourage casual copying and to keep the internal font program tidy; the algorithm is well documented, and font tools decrypt it routinely. Inside, a Type 1 font is really a small PostScript program that a printer or rasterizer executes to produce outlines.

The binary in Printer Font Binary distinguishes it from its sibling, the PFA (Printer Font ASCII). The two carry the same font; PFB stores the data as compact binary segments with length markers, while PFA encodes everything as printable hexadecimal text so it can pass safely through systems that only handled ASCII. PFB is smaller and was the usual form on Windows, whereas classic Mac systems stored Type 1 outlines differently again, in resource forks.

Crucially, a PFB is only half of a Type 1 font. It holds the outlines, but the metrics (the width of each character and the kerning between pairs) live in a separate AFM or PFM file. An application needs both parts to set type correctly. This two-file design, sensible in the 1980s, later became one of the format's biggest practical liabilities because the pieces could be separated or lost.

History and Standardization

Type 1 was created by Adobe in the mid-1980s alongside the PostScript page-description language, and it powered the desktop publishing revolution. When a document was printed, the printer's PostScript interpreter used the Type 1 outlines to render crisp text at the device's full resolution, a dramatic improvement over the bitmap fonts of the time. For roughly a decade, professional publishing ran on Type 1, and the PFB was how those fonts lived on a PC.

Adobe initially kept the Type 1 specification proprietary, publishing the details only after Apple and Microsoft developed TrueType as an open alternative in the early 1990s. Adobe then released the Type 1 specification publicly, but the competitive pressure had already set the industry on a path toward a unified successor. The metrics, encoding, and outline conventions of Type 1 were widely implemented, though the format was defined by Adobe's specification rather than by an international standards body.

That successor was OpenType, which absorbed Type 1's cubic outline technology into its Compact Font Format table, letting foundries carry their designs forward in a single modern file. The migration was decisive: Adobe ended authoring support for Type 1 in its Creative Cloud applications, meaning PFB fonts can no longer be used to set new type in current professional software. The format is now firmly legacy, valued mainly for archival and historical continuity.

PFB Compared to OpenType and TrueType

Against OpenType, PFB is comprehensively outmatched. Type 1 fonts are capped at 256 characters, split across two files, and carry none of the ligature, alternate, and script-shaping logic that OpenType provides through its GSUB and GPOS tables. The one thing PFB fonts hold that survives is their cubic outlines, and OpenType's CFF flavour preserves exactly that curve technology, which is why converting a Type 1 font to OpenType is largely lossless for the shapes themselves.

Against TrueType, the difference is mostly the curve mathematics: Type 1 and CFF use cubic Bezier curves, while TrueType uses quadratic ones. Cubic curves need fewer points to describe a given shape, which many type designers preferred, whereas TrueType's quadratic outlines paired with its detailed hinting instructions historically rendered very sharply on low-resolution screens. Both approaches now coexist inside OpenType, so the rivalry is settled rather than ongoing.

For anyone holding a library of PFB fonts today, the practical advice is to convert them to OpenType before the tooling disappears, keeping the original PFB and its AFM metrics as an archive. A modern workflow cannot reliably set type from a raw PFB, and the separate metrics file is easy to misplace. The format is worth understanding as the direct ancestor of today's fonts, but not as something to build new work on.