Configuration

<config> sits at the top of a document and sets things up before any content. Its children are all optional:

• <page size= margin=> — defaults inherited by every <page> in <pages>. Sizes are A3, A4, A5, A6, Letter, or Legal (case-insensitive); a per-page attribute overrides the default for that page. Omit size and pages default to A4. margin takes the CSS 1–4 value shorthand — margin="0" (all sides), "20px 40px" (vertical / horizontal), or "10px 20px 30px 40px" (top / right / bottom / left); omit it and every edge gets 36pt (half an inch).
• <meta name= value=> — written into the PDF's Info dictionary (title, author, …). Both attributes are required; repeat the tag for as many pairs as you like.
• <defaults> — per-tag attribute defaults (see below).
• <font-face> / <google-font> — register custom font families (see Fonts below).
• <fonts subset=> — font subsetting is on by default (only the glyphs you use are embedded). Set subset="false" to embed full faces.
• <diagnostics mode=> — how the engine treats errors. mode="warn" (the default) reports every recovered problem yet still produces a PDF; mode="strict" refuses to write output if any error was recorded (content dropped because it couldn't fit a page, a required attribute missing). Warnings never block in either mode. Use strict in a build pipeline to fail the build on lost content.

Defaults

A <defaults> block declares the attribute values a tag should assume when an instance leaves them out — <text font="merriweather" size="11"/> makes every <text> default to that face and size. A block in <config> is document-wide, but blocks also nest inside a page or any container and apply positionally, so an attribute resolves element attribute → nearest enclosing <defaults> → config defaults → system default. The Defaults guide covers the full positional and scoping rules; style:* attributes are resolved separately and aren't defaulted.

Fonts

The built-ins are sans (the default) and serif, embedded so output looks the same everywhere — they're the metric-compatible Liberation faces (Arial- and Georgia-metric), so a document falls back to a familiar shape on any platform. Register more in two ways:

• <font-face name= src= [bold] [italic] [serif]/> points a family at a local font file (.ttf or .woff2), resolved relative to the document. One declaration per face — repeat with bold/italic to add weights and styles to the same name. Reusing a built-in name (e.g. name="sans" bold) swaps just that one face.
• <google-font name= [serif]/> pulls a family straight from Google Fonts by its name — no local files. Its regular, bold, italic, and bold-italic faces are fetched automatically and the family is used (lowercased) via font="…". serif hints the fallback for families with serifs. The CLI downloads and caches the faces to embed them; this browser preview loads them from the Google Fonts API.