Modules reference
Baseline ships as five feature modules. Each one wires a distinct concern into Eleventy and stays out of the way of the others. The pages below cover what each module does, when it activates, and the options it accepts.
If you are starting out, how Baseline works introduces the three-layer model these modules sit on top of. The tutorial walks through the common pairings.
The five modules
The assets module: PostCSS and esbuild: wires JS (esbuild) and CSS (PostCSS) entry points into Eleventy, with inline filters for critical-path assets.
The head module and baseline-head: replaces a <baseline-head> placeholder with a sorted, deduped element list at transform-time.
The multilang module: hreflang and locales: language normalisation, per-page lang and locale, page.translations, and the translation filters. Opt-in.
The navigator module and debug page: runtime-introspection surface and public read surface. A phpinfo()-style virtual page for current build state, the globals and filters used to build it, and the _navigator global ({ nodes, edges, backlinks }) for cross-page reads of the content graph.
The sitemap module: drafts and exclusions: a single /sitemap.xml, or per-language sitemaps plus an index when multilang is active.