fpgm

The fpgm table, short for font program, is a component of TrueType font files. It contains a sequence of bytecode instructions written for the TrueType virtual machine. The instructions in the fpgm table are executed by the font rasterizer to initialize and configure global hinting parameters that influence how glyph outlines are grid-fitted and rendered.

The primary purpose of the fpgm table is to set up the font’s global hinting environment. It can adjust the control value table (CVT) and other state that affects all glyphs, providing a consistent hinting baseline across the font. The fpgm program runs when the font is loaded, before per-glyph processing takes place. In contrast, per-glyph hinting is largely handled by the prep table, which contains its own bytecode executed for each glyph during rendering.

Not all fonts include an fpgm table. It is optional, and modern OpenType fonts with PostScript outlines or with simplified hinting may omit it altogether. When present, the fpgm table works in concert with other TrueType tables such as cvt, glyf, head, hhea, and hmtx to enable the font’s hinting behavior. Tools that inspect or edit fonts can reveal the fpgm content; changes to this program can significantly affect rendering, particularly at small sizes or on lower-resolution displays.

In summary, fpgm is the font program table in TrueType fonts, housing global hinting instructions that influence how glyphs are prepared for rendering, in collaboration with the per-glyph prep program and other font tables.