sup-xml

A memory-safe, fast, spec-compliant XML toolkit for Rust — parsing, serialization, XPath, XSD, XSLT, RelaxNG, Schematron, C14N, and HTML5 in one library, with a clean idiomatic API and no unsafe in your way.

This crate (sup-xml) is the idiomatic Rust API. The same engine also ships as a drop-in libxml2 ABI replacement for code that links libxml2 today (C/C++, Python lxml, Ruby nokogiri, Perl XML::LibXML).

• Memory-safe — pure Rust with a small, audited unsafe core, enforced by #![forbid(unsafe_code)] everywhere else and exercised under Miri in CI.
• Spec-compliant — 255 / 257 on the W3C XML Conformance Test Suite, ahead of libxml2's 250 / 257.
• Fast — roughly 2× libxml2 and ~1.04× quick-xml on matched-contract byte-event throughput.

Install

[dependencies]
sup-xml = "1.0"

# Optional features — pull in only what you need:
sup-xml = { version = "1.0", features = ["xsd", "xslt", "html"] }

Requires Rust 1.85+ (edition = "2024").

Quick start

use sup_xml::{parse_str, ParseOptions, XPathContext};

let opts = ParseOptions { namespace_aware: true, ..Default::default() };
let doc = parse_str("<catalog><book id='b1'/><book id='b2'/></catalog>", &opts)?;

let ctx = XPathContext::new(&doc);
assert_eq!(ctx.eval_count("/catalog/book")?, 2);
# Ok::<(), sup_xml::Error>(())

Features

License

SupXML is source-available software released through Supported Source. The source is public and this crate installs normally, but a valid license certificate is required to use it — without one, document parsing returns a fatal error (a grace period applies after an existing certificate expires).

Get a certificate at supso.org/projects/sup-xml and place it where SupXML looks — ~/.supso/license_certificates/ or a project-local ./.supso/license_certificates/. Full terms are in the repository LICENSE.

Documentation

• Project docs
• API reference (docs.rs)
• Source on GitHub