Compatibility

NetPdf implements a curated, print-focused subset of HTML and CSS. The goal is faithful, deterministic paged output — not parity with an interactive browser. This page summarizes what's in and out of scope; the authoritative, feature-by-feature matrix is docs/compatibility-matrix.md.

Rendering fidelity — what to expect

NetPdf does not aim to render identically to a web browser, and it deliberately doesn't try to. It is a print- and paged-media engine: its purpose is to turn document-shaped HTML and CSS into well-formed, deterministic PDFs, not to reproduce a browser's on-screen rendering pixel-for-pixel.

For the content it is built for — invoices, statements, reports, letters, certificates, and similar documents — NetPdf targets close visual parity with a browser's print output (the result of the browser's "Print → Save as PDF"), a different and more constrained target than interactive on-screen layout.

"Renders identically to any browser" is therefore not a claim NetPdf makes. Screen-oriented or interactive layouts, scripted content, and pixel-exact matching of a specific browser engine are out of scope. Where a feature falls outside that scope, NetPdf emits a stable, structured diagnostic rather than silently approximating or dropping content, so the places where output differs are explicit rather than surprising.

Status legend

Meaning
✅ Supported Fully implemented and tested.
🧪 Partial Implemented with documented caveats.
📥 Parsed only Grammar accepted; rendering pending; emits a stable diagnostic.
❌ Out of scope Not rendered for v1; emits a diagnostic (content is never dropped silently).

In scope

  • Layout — block, inline, flex, grid (Level 1), tables, and multi-column, all fragmentation-aware across pages.
  • Paged media — @page, the 16 margin boxes, running headers/footers via string() / element(), counter(page), orphans / widows, and break-before / break-after / break-inside.
  • Visual — gradients (linear / radial / conic), box- and text-shadows, 2-D transforms, borders + border-radius + border-image, clip-path, multi-layer backgrounds, opacity, and CSS filters on images.
  • Text — HarfBuzz shaping, bidi (UAX #9), line breaking (UAX #14), and hyphens: auto with language routing via the language packs.
  • Images — data: URIs inline (no network by default); PNG / JPEG native, other formats via the Skia raster fallback; object-fit / object-position.
  • SVG — a static subset, rendered natively (with a raster fallback where needed).
  • Links — <a href> becomes a PDF Link annotation.

Out of scope for v1

  • JavaScript — <script> never executes (emits HTML-SCRIPT-IGNORED-001). This means CDN-based Tailwind and other runtime-CSS tools won't work; pre-compile your CSS to static output.
  • <form> widgets, <video> / <audio>, <iframe>, <canvas>, <object> / <embed>.
  • CSS animations / transitions (no timeline in a static document).

Anything unsupported emits a stable diagnostic code rather than silently corrupting output.

Accessibility (PDF/UA)

Tagged-PDF / PDF/UA-1 emission is not yet produced; it is on the post-1.0 roadmap.