On November 24, 2022, SWI-Prolog 9 has been released. By incrementing the major version we consolidate a development cycle of about three and a half year. More than half of this development was carried out in SWI-Prolog Solutions b.v. The highlights are below. The complete list of changes is long. The 8.x series adds and improves a lot of functionality while providing good backward compatibility.

• Mature and feature-rich tabling support including well founded semantics, incremental tabling, monotonic tabling and shared tabling.
• Single sided unification [SSU](/pldoc/man?section=ssu) and zero-cost runtime determinism checking. See also $/0, $/1 and det/1.
• Database transactions see transaction/1 and snapshot/1.
• A new C++ interface that covers the whole foreign API and provides much better type safety.
• Linux versions are by default linked to tcmalloc. This provides more information and control and reduces the footprint of multi-threaded 7x7 servers considerably compared to the default ptmalloc.
• Interfaces to Redis and STOMP message passing systems.
• A port to WASM WebAssembly allows running SWI-Prolog in the browser. The high level bi-directional interfaces to JavaScript allows for inspecting and modifying the browser DOM.
• A completely new GNU-Emacs package called sweep. Sweep embeds Prolog, which allows for semantic highlighting and much more.
• A bundled replacement for GMP, providing unbounded integers and rational numbers based on LibBF under a permissive license. Currently significantly slower on notably larger rational numbers.

Thanks to all those who contributed code, documentation, feedback, bug reports, etc. Without you this release would not have been possible.