XSL-FO processors

XSL-FO processors are really typesetting engines. An XSL-FO file is a mixture of text from your XML source document and XSL-FO tags that suggest how the text should be formatted. It is the XSL-FO processor that actually creates the typeset lines of text and lays them out on pages. An XSL-FO processor typically generates a PDF or PostScript file which can be fed to a printer to produce hardcopy output.

Currently there are many XSL-FO processors, but few of them have completely implemented the standard. There are at least three reasons for this:

The authors of the XSL-FO standard recognized how difficult it would be to implement, and so divided it into three levels of conformance: basic, extended, and complete. That way a processor can claim conformance to the lower conformance levels and produce useful output, while still be under development for the higher conformance levels.

Here are some of the currently available XSL-FO processors, listed in alphabetical order. FOP, PassiveTeX, and xmlroff are the free processors, but the commercial products implement more of the XSL-FO standard.


High end publishing server from Arbortext, Inc. (http://www.arbortext.com). It runs on Windows and Unix.


FOP is a Java-based processor available free from the Apache XML Project (http://xml.apache.org/fop/). FOP can produce usable output, but it is still under development and has some limitations. It eventually will be able to produce many forms of output beyond the current PDF.


PassiveTeX from Sebastian Rahtz (http://www.tei-c.org.uk/Software/passivetex/) is a free XSL-FO processor based on TeX. It has fallen behind in its implementation of the XSL-FO specification, and many features of DocBook XSL don't work in PassiveTeX.

Unicorn Formatting Objects

A commercial product from Unicorn Enterprises SA (http://www.unicorn-enterprises.com). For Windows only.


A commercial product from RenderX (http://www.renderx.com). It is a Java-based product that runs on most platforms.


A commercial product from Lunasil LTD (http://www.lunasil.com/). It is a Java-based product that runs on Linux and Windows.


A commercial product from Altsoft (http://www.alt-soft.com/). For Windows only.

XML Professional Publisher (XPP)

A high-end XML publishing environment from XyEnterprise (http://www.xyenterprise.com/). It runs on Windows and Unix.


xmlroff (http://xmlroff.sourceforge.net/) is a free open source project based on libxml2 and other GNOME libraries. It is written in C.

XSL Formatter

A commercial product from Antenna House (http://www.antennahouse.com). It runs on Windows, Unix, and Linux.

Other XSL-FO processors are listed on the W3C's XSL information page.