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Press.js

Press.js is a browser-based layout engine for generating high-quality PDFs from web UIs. Instead of translating a design into a proprietary PDF drawing API, Press.js captures live HTML/CSS rendered in a headless Chromium browser and re-paginates it into a professional document layout.

Why Press.js?

Section titled “Why Press.js?”

Traditional PDF libraries require you to learn a new set of layout primitives — draw commands, coordinate systems, and positioning APIs. Press.js lets you use the tools you already know:

  • Standard HTML and CSS — style your documents with the same CSS you use for web apps
  • Your favorite framework — first-class support for React and Vue, with semantic components that mark up your document structure
  • Full power of the web — SVG charts, Canvas visualizations, tables, custom fonts, and any DOM API

How it works

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Press.js runs in three phases at render time:

  1. Ghost measurement — the runtime clones your live DOM, measures every element’s dimensions, and classifies nodes (block, table, atomic, header, footer, page-break)
  2. Fragmentation planning — the core algorithm creates a page-by-page plan, deciding which content fits on each page. Tables are split row-by-row, blocks are split recursively, and oversized nodes are flagged
  3. Materialization — the plan is realized as actual paginated output, then exported to PDF via Chromium’s print engine

During development, the Preview system gives you real-time feedback by running the full pagination pipeline in your browser.

During PDF rendering, Press.js disables browser CORS and CSP enforcement in the headless Chromium page. Cross-origin requests for stylesheets, images, fonts, scripts, and API data are not blocked by missing CORS headers; the resource only needs to be reachable from the rendering environment.

Current status

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Press.js is in early development. The core APIs are functional and actively used in production, but you may encounter rough edges. Please report issues on GitHub.

Next steps

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