Historically, the graphics library upon which MuPDF relies was known as ‘fitz’. Accordingly, all MuPDF’s API calls and most types start with ‘fz_’.
The exception to this is where we have APIs and types provided by particular format handlers (e.g. PDF or XPS). These functions/types are prefixed with the format handlers name, for example ‘pdf_’ or ‘xps_’.
All exported functions and types should be prefixed in this way to avoid the possibility of clashing with symbols in calling applications. Internal functions are not required to be prefixed, but we encourage it for clarity.