Compare · Apache FOP
XML2PDF Core and Apache FOP.
FOP is a mature, free, Apache-licensed XSL-FO implementation that runs on the JVM. This page compares the two on seven criteria so a Windows/.NET team can decide — including when FOP is the better answer.
For many teams, Apache FOP is the right choice.
FOP is free, actively maintained, licensed under Apache 2.0, and runs anywhere a JVM runs. Its feature surface is far broader than ours, and its documentation reports compliance in more detail than anything we can currently show.
FOP's own documentation is candid about the same subject: the project "does not currently conform to any of these [compliance] levels" and describes itself as "a useful work-in-progress".
Read the source
xmlgraphics.apache.org/fop/What our corpus rendersNeither project publishes a shared benchmark, so this page compares structure, not speed.
The seven criteria
Seven criteria, no scoring.
| Criterion | Apache FOP | XML2PDF Core |
|---|---|---|
| XSL-FO rendering | Apache FOPYes — driven by XSL-FO; the reference open-source implementation. It publishes a per-level compliance table rather than claiming conformance. | XML2PDF CoreYes — XSL-FO in, PDF out, evidenced by a 22-fixture regression corpus, not a conformance claim. |
| Native .NET integration | Apache FOPNo — a Java application; called from .NET through a JVM bridge or a separate process. | XML2PDF CoreYes — a .NET class library, called in-process. |
| Java requirement | Apache FOPRequired. | XML2PDF CoreNone. |
| Platform compatibility | Apache FOPAny platform with a JVM. | XML2PDF CoreWindows x64, .NET 10 only — net10.0-windows. |
| Evaluation model | Apache FOPFree and unrestricted — it is Apache 2.0. | XML2PDF CoreFree and unlimited, watermarked on every page, no registration, no key. |
| Licensing | Apache FOPApache License 2.0. | XML2PDF CoreCommercial $999 one-time per company — Commercial and OEM in one licence, royalty-free embedding, 12 months of released updates, perpetual; free Evaluation edition. |
| Price | Apache FOP$0 | XML2PDF Core$999 one-time |
Choose FOP if…
- You deploy on Linux or macOS, or already run a JVM in production — FOP asks for nothing more than a Java runtime.
- You need the broadest XSL-FO feature surface available today, including constructs this library does not implement.
- You want a zero-cost, Apache-2.0 dependency with a large community and a long release history.
None of these is a blocker for most FOP users — which is why it stays the right default for many teams.
Choose XML2PDF Core if…
- Your application is a Windows x64 .NET 10 build and you would rather not ship a JVM.
- You want the renderer in-process: no bridge, no sidecar, no extra process to monitor.
- A single $999 licence for the whole company fits your procurement better than a support contract.
Sources: prices and licence facts from each project's own site, checked November 2026. FOP quotes from its documentation at xmlgraphics.apache.org/fop/. No speed, accuracy or conformance comparison is implied — none has been measured.