Supported HTML and CSS

Documents are laid out for paper: pages, tables that continue across pages, headers and footers. The service supports the parts of HTML and CSS that matter for that. Anything outside it is ignored and reported by validation.

Layout

The CSS box model, with box-sizing, margins (including auto and negative), min- and max- sizes.
Tables, including colspan, rowspan, and header rows repeated on every page they span.
Flexbox: direction, wrap, grow, shrink, basis, align-* and justify-content.
A subset of grid: grid-template-columns with lengths, fr, auto and repeat(), and gap, with automatic row placement.
display: inline-block, multi-column text (column-count, column-gap), lists with markers, <hr>.
position: relative and absolute with offsets, and z-index.

Paged media

@page size, orientation and margins, and top and bottom margin boxes for headers and footers, with counter(page) and counter(pages).
break-before, break-after, break-inside and the older page-break-* names, with widow and orphan control.
A PDF outline built from headings, and clickable links from <a href>.

Text

Shaping for complex scripts and right-to-left text.
font-weight from 1 to 1000 and italic, for fonts that have those styles.
hyphens: manual, and automatic hyphenation for English.
Units px, pt, cm, mm, in, %, em and rem, and calc().

Painting

Colors, backgrounds, linear-gradient(), borders (solid, dashed, dotted), border-radius, box-shadow, opacity, and overflow: hidden.
SVG rect, circle and line, drawn as vector shapes.
PNG and JPEG images; see Images.

Selectors and variables

Tag, class, id, universal, attribute selectors with the common operators, descendant, child and sibling combinators, :nth-child, :first-child and :last-child. CSS custom properties with var() and fallbacks.

Not supported

JavaScript, @font-face and @import, animations and transitions, pseudo-classes such as :hover, and most of what only makes sense on a screen. If you are unsure, validate the document.