Limitations

PdfPecker is built for fast conversion of HTML templates you control, not for rendering arbitrary web pages. These are the known gaps; most are scope choices for speed and size, and they are the first candidates for future work. Anything not listed in What is supported should be assumed missing.

By design

• No JavaScript. Scripts are never run, so content must be in the HTML before conversion (render it server-side first).
• No network access: http:/https: stylesheets and images are not downloaded. Supply them through your ResourceResolver, as files under BaseDirectory, or as data: URIs.
• <canvas>, <iframe>, <video>, <audio>, <object> and <embed> are not drawn, nor are file, range, colour and image inputs. Form fields have no JavaScript (no calculations, formats or submit actions), and a field inside a transformed box, a running header or footer, or a position: fixed box is drawn but not fillable.

Text and fonts

• Without registered fonts or EmbedStandardFonts, text uses the standard PDF fonts, so characters are limited to the Windows-1252 set (Western European languages); other characters are replaced with ?. The bundled Liberation fonts add Central European, Greek and Cyrillic, but not CJK or other scripts: register fonts for those.
• Complex-script shaping covers Arabic and Hebrew (and other scripts written with Arabic letters, such as Persian and Urdu). Devanagari and other Indic scripts, Thai, Khmer, Myanmar and Syriac are not shaped, so their vowel signs and conjuncts come out wrong, and Thai text breaks only at spaces. There is no vertical text (writing-mode).
• In Latin and other simple scripts, shaping is limited to pair kerning and standard ligatures; no contextual alternates or other OpenType features (small-caps is synthesized from scaled capitals).
• Variable fonts use their default instance (font-variation-settings and font-stretch are ignored).
• Automatic hyphenation (hyphens: auto) has built-in patterns for English, Danish, German, Dutch and Norwegian only; other languages need their patterns in PdfOptions.Hyphenation. hyphenate-limit-chars is not supported.
• SVG <text> uses only the first value of position lists and has no textPath; in a text chunk with right-to-left text, dx on its tspans is ignored.

CSS

• A table column width that mixes a percentage with other units (calc(50% - 10px)) is sized as auto.
• @import is ignored (use <link rel="stylesheet">), and rules inside @container blocks are skipped. @page rules for :first, :left and :right pages can style margin boxes but not change the page size or margins. A named page's :first is the document's first page, as in Chrome, not the first page of the named run.
• Selectors: no ::first-letter/::first-line. A rule with an unsupported selector is skipped. :hover, :focus and similar interaction states never match. Selectors inside :is(), :where() and :not() may have at most eight compound parts (one when nested in another of them).
• Properties not supported: filter, mix-blend-mode, clip-path on HTML elements (only in SVG), border-image, list-style-image, font-variant-numeric and inset box-shadow. No relative colours (rgb(from …)).
• text-shadow blur is approximated with faint copies of the text rather than a true Gaussian blur, and decorations (underlines) get no shadow. text-overflow only supports ellipsis at the end of the line (clip and custom strings do nothing). aspect-ratio does not take part in min-/max-content sizing (shrink-to-fit widths) and is ignored on tables. object-fit applies to raster images; an SVG file in <img> keeps its own preserveAspectRatio fit.
• Borders: groove, ridge, inset and outset draw as solid.
• position: sticky is drawn as relative; background-attachment: fixed scrolls with the box.
• Lists: list-style-type covers disc, circle, square, decimal, decimal-leading-zero, alpha, roman and strings only (no Greek, CJK or @counter-style).

Backgrounds and transparency

• No background-clip: text; backgrounds of inline elements (<span>) show only their colour, not images or gradients.
• Blurred box shadows and repeating gradients with translucent stops are blended onto the background colour rather than truly see-through; SVG gradient stops with transparency are blended onto white.

Layout

• Grid: no subgrid.
• Multi-column: children are kept whole and balanced between columns; a single block is never split across columns.
• Overflow: a positioned child with a z-index inside a clipping box stays stacked within that box.

Images and SVG

• Images: no AVIF, BMP or TIFF. Animated GIF and WebP files show only their first frame.
• SVG (inline and files): no embedded <image>. Filters have no feTurbulence, feImage, feTile, feConvolveMatrix, feDisplacementMap or lighting (these pass their input through unchanged) and ignore primitive subregions; filtered content becomes an image (text in it is no longer selectable). Watermark images must be raster images (PNG, JPEG, GIF or WebP).

Markdown and the PDF renderer

• Markdown: no footnotes, definition lists, math or front matter.
• PdfRenderer (PDF to image): no predefined CJK CMaps or non-embedded CJK fonts, and ICC profiles are not applied (ICC-based colours use their device equivalents). WebP output is lossless only (no lossy VP8), and JPEG output is baseline only (no progressive or arithmetic coding).