HTML and CSS support

Changed in 1.16.0: CSS properties, Pagination, SVG.

PdfPecker lays out HTML and CSS the way Chrome prints it. Anything not listed here should be assumed missing; the known gaps are listed under Limitations.

HTML

The common document elements: headings, paragraphs, div/section-style blocks, span, a (external links and #id links inside the document), b/strong, i/em, u, s, sub, sup, small, big, mark, code, pre, blockquote, hr, br, ul/ol/li (nested, with start and value), dl, table (with thead, tbody, tfoot, caption, colspan, rowspan, col width), img, inline <svg>, and legacy attributes such as align, valign, bgcolor, width, height, border, cellpadding, cellspacing and <font>. The dir attribute (ltr, rtl and auto), <bdi> and <bdo> set the text direction. The parser is forgiving about unclosed and misnested tags, the way browsers are.

Markdown is converted to this HTML first; see Markdown.

CSS

<style> blocks, <link rel="stylesheet">, @import (with layer(), supports() and media queries; a relative URL is relative to the importing stylesheet), inline style attributes, @media (media queries level 4: print, width/height and orientation of the page area, ranges such as (400px <= width <= 800px), and, or, not), @supports (property tests, selector(), and/or/not), @layer cascade layers, CSS nesting (&), @property (initial values and inheritance of registered custom properties), @container (see Container queries) and @page (see Paged media). Selectors: type, .class, #id, *, attribute selectors ([a], =, ~=, |=, ^=, $=, *=, with i/s flags), descendant, >, +, ~, :first-child, :last-child, :only-child, :nth-child() and :nth-last-child() (incl. of S), :first-of-type, :last-of-type, :only-of-type, :nth-of-type(), :nth-last-of-type(), :not(), :is(), :where() and :has() (all with lists of complex selectors, such as :is(nav > a, .menu li), nested to any sensible depth; :is() and :where() skip entries they do not understand), :root, :link, :empty, :lang(), form states (:checked, :disabled, :enabled, :required, :optional, :read-only, :placeholder-shown and the like), ::before, ::after, ::marker, ::first-letter (drop caps, floated or not) and ::first-line, with specificity and !important handled as in browsers. As when Chrome prints, interaction states such as :hover and :focus never match.

CSS properties Changed in 1.16.0

Units and colours

Units: px, pt, em, rem, %, mm, cm, in, pc, ex, ch, vw, vh, vmin, vmax (the viewport is the page's content area, minus any running header and footer, in whole pixels as in Chrome), and the container query units cqw, cqh, cqi, cqb, cqmin and cqmax. Colours: names, #rgb, #rrggbb, #rrggbbaa, rgb(), rgba(), hsl(), hsla() (comma or space syntax), hwb(), lab(), lch(), oklab(), oklch(), color() (sRGB, Display P3 and the other predefined spaces, mapped to sRGB), color-mix(), light-dark() (the light value), currentColor, and relative colours (rgb(from var(--brand) r g b / 50%), oklch(from teal calc(l + 0.1) c h) and the like, in every colour function, with the channels usable in math functions).

Subgrid

grid-template-columns: subgrid and grid-template-rows: subgrid (CSS Grid Level 2) let a grid item that is itself a grid share its parent's tracks on that axis, so the rows of nested cards or the columns of a form line up across the whole grid. The subgrid's items take part in sizing the parent's tracks, gaps come from the parent unless the subgrid sets its own, and line names come from the parent and from the subgrid's own list (including repeat() and repeat(auto-fill, …)). Subgrids nest, and a subgrid that is not a grid item is laid out as none, as in browsers. Rows paginate as the parent grid's rows do.

.plans { display: grid; grid-template-columns: repeat(3, 1fr); gap: 16px }
.plan { display: grid; grid-row: span 3; grid-template-rows: subgrid }   /* title, features and price line up */

Multi-column layout

column-count, column-width and columns lay content out the way Chrome does. Paragraphs, lists, tables and other boxes continue from one column into the next, every column on every page is filled, and the last row of columns is balanced (column-fill: balance) or filled in turn (column-fill: auto). column-span: all, column-gap, column-rule, break-before/break-after: column, break-inside: avoid and avoid-column, orphans and widows, repeated table headers and right-to-left columns work as in Chrome, which also ignores break-before: page inside columns.

Percentage heights

Percentage height, min-height and max-height resolve as in browsers when the containing block's height is definite: a length, a chain of percentages up to the page (html, body { height: 100% }), a stretched flex or grid item, a flex item grown in a container of definite height, an aspect-ratio height, or the padding box for absolutely positioned boxes. Children of a table cell resolve against it when the cell has a fixed height or the table has a height. Against an auto height a percentage behaves as auto, as in browsers.

Container queries

container-type (inline-size or size), container-name and the container shorthand make an element a query container, and @container rules style its descendants by the container's size: width, height, inline-size, block-size, aspect-ratio and orientation, with min-/max- prefixes or range syntax, combined with and, or and not. A name picks a container (@container sidebar (width < 300px)), and style(--compact: 1) queries a custom property. The cq units are percentages of the nearest container's size. One component can then lay itself out for a narrow sidebar and a wide main column without knowing where it is placed.

.card-slot { container: card / inline-size }
.card { display: grid; gap: 8px }
@container card (width >= 400px) { .card { grid-template-columns: 120px 1fr } }
.card h3 { font-size: clamp(14px, 5cqi, 22px) }

A document that uses container queries is laid out again until the container sizes settle, which takes about two to four times as long; documents without them are laid out as before.

Pagination Changed in 1.16.0

Lines, images and table rows are never cut in half at a page boundary; table header rows repeat at the top and <tfoot> rows at the bottom of every page a table spans, as in Chrome; backgrounds and borders continue across pages. Flex lines move to the next page as a whole when they don't fit. A grid row breaks across the page boundary where it starts, as in Chrome, and moves whole only when one of its items cannot break (a line of text, an image, or a box with break-inside: avoid). A table inside a flex or grid item breaks across pages like any other table, with its header repeated, and the line or row grows to match. A paragraph that splits leaves at least orphans lines (default 2) at the bottom of a page and carries at least widows lines (default 2) to the next. Headings keep with the content that follows them (break-after: avoid in the default styles), and break-before/break-after: avoid does the same for any block. break-inside: avoid keeps a block or a whole table on one page when it fits. As in Chrome, a margin that runs past the end of a page is dropped rather than carried to the next one (except after a forced break), and a box's top and bottom borders and padding stay on the same page as its first and last content.

Links and bookmarks

<a href> becomes a clickable link, whether inline or a block (a card wrapped in a link), and stays clickable on both pages when a page break splits it. External URLs open in the viewer's browser and #id links jump to the element. Headings h1-h6 become the PDF's bookmarks, nested by level; set PdfOptions.Bookmarks = false to leave them out.

SVG Changed in 1.16.0

Inline <svg> and SVG files (in <img> and as url() backgrounds, including data:image/svg+xml URIs) with path (all commands, arcs included), rect (incl. rounded), circle, ellipse, line, polyline, polygon, text and tspan (x, y, dx, dy, text-anchor, dominant-baseline, direction, registered fonts and right-to-left text), textPath (text along a path, with startOffset and the path's pathLength, as in Chrome), g, use, nested svg, image (raster images and SVG files, with preserveAspectRatio; inside an SVG file only data: URIs load, as in browsers), viewBox, preserveAspectRatio and transform, drawn as vector paths. Strokes can be dashed with stroke-dasharray and stroke-dashoffset, scaled by pathLength. linearGradient and radialGradient (both units, gradientTransform, spreadMethod, href inheritance, and stop-opacity that is truly transparent) become PDF shadings, and pattern fills and strokes (both units, viewBox, patternTransform, href inheritance) become PDF tiling patterns. clipPath clips the elements that reference it, and mask (luminance or alpha, both units) becomes a PDF soft mask. marker draws arrowheads and dots at the vertices of paths, lines, polylines and polygons (orient incl. auto and auto-start-reverse, markerUnits, viewBox, refX/refY, clipped to the marker unless overflow="visible"). filter is applied in pixels, at 144 dpi, and drawn as an image, with every filter primitive: feGaussianBlur, feOffset, feDropShadow, feFlood, feMerge, feComposite (all operators), feBlend (separable modes), feColorMatrix, feComponentTransfer, feMorphology, feTurbulence, feImage, feTile, feConvolveMatrix, feDisplacementMap, and feDiffuseLighting and feSpecularLighting with distant, point and spot lights and lighting-color, in linearRGB or sRGB. Primitive subregions (x, y, width, height) work as in Chrome. Text under a filter stays selectable and searchable: an invisible copy of it is kept on top of the image. As in browsers, an SVG file is styled only by its own <style> elements and attributes, not by the page's CSS, and loads nothing else.

Images

JPEG (embedded as-is, RGB, grayscale and CMYK), PNG (all colour types and bit depths, transparency, interlacing), GIF (transparency, interlacing), WebP (lossy, lossless and with alpha), BMP (1 to 32 bits, palettes, RLE, bit fields and alpha) and TIFF (uncompressed, LZW, Deflate, PackBits, CCITT G3 and G4, JPEG; strips or tiles, planar, alpha, 16-bit; bilevel images stay 1 bit per pixel), from files, data: URIs or your ResourceResolver. Animated GIF and WebP files show their first frame, as a PDF page is still. SVG files are drawn as vectors (see SVG above). Opaque PNGs are passed through without re-encoding. Images wider than the page are scaled down to fit.