FontForge (originally PfaEdit) is an open source font editor primarily. It is available for several operating systems (including Linux, Windows and Mac OS X) and is localized into 12 languages. The main developer of the app is George Williams. FontForge supports a wide variety of font formats. Its native Spline Font Database format (.sfd file name extension) is text-based and facilitates collaboration between designers, as difference files can be easily created. FontForge also supports the interoperable UFO source format, which is based on XML. The software supports many other font formats and converts fonts from one format to another. Supported font formats include: TrueType (TTF), TrueType Collection (TTC), OpenType (OTF), PostScript Type 1, TeX Bitmap Fonts, X11 OTB bitmap (only sfnt), Glyph Bitmap Distribution Format (BDF), FON (Windows), FNT (Windows), and Web Open Font Format (WOFF). FontForge also imports and exports fonts to and from the Scalable Vector Graphics (SVG) format and the Unified Font Object (UFO) format.