ParaPDF

A fast PDF viewer for React, built on pdf.js: React out of the hot path, and drawing off the main thread wherever pdf.js allows it.

The name combines the Japanese "parapara", flipping quickly through pages, with parallel rendering on worker threads.

Status: 0.x. parapdf is on npm, and its API may change in any minor release until 1.0.

npm install parapdf

import { PdfDocument, PdfViewer } from "parapdf";

export function App() {
  return (
    <PdfDocument source="/manual.pdf">
      <PdfViewer style={{ height: "100vh" }} />
    </PdfDocument>
  );
}

parapdf.yhay81.com has the guides, the API reference, and a live demo. CHANGELOG.md lists the releases.

What it is

• React stays out of the hot path. Scrolling and zooming commit no React state per frame, and pixels never pass through React.
• Only what is near the viewport exists. Pages outside a small window unmount, draw a quick base first and full resolution once scrolling settles, and keep their canvases within a budget so a page the reader comes back to shows at once.
• Viewers of their own. Several viewers and thumbnails share one open document, each with its own position, zoom, rotation, and layout.
• A document viewer. Selectable, accessible text, search, links and the outline, forms, annotations, printing, saving, layers, attachments, and encrypted documents. Each feature is a module only applications using it load.
• pdf.js included. The package ships pdf.js's worker and the files it loads on demand, so applications configure nothing.

Every choice that may affect speed or memory is measured; the performance page has the numbers, and docs/decisions/ the records behind them.

Develop it

A pnpm workspace for Node 24 or later: the package in packages/parapdf, the demo with its functional checks and benchmarks in examples/prototype, the engine benchmark in bench, and the documentation site in site. docs/architecture.md describes the design, AGENTS.md the layout and commands, CONTRIBUTING.md what a pull request needs, and SECURITY.md how to report a vulnerability.

pnpm install
pnpm check
pnpm test
pnpm --filter @parapdf/bench exec playwright install chromium webkit firefox
pnpm --filter @parapdf/bench corpus
pnpm --filter @parapdf/prototype build
ENGINE=pdfjs pnpm --filter @parapdf/prototype check:text

License

Apache License 2.0. Parts of ParaPDF are derived from pdf.js: see NOTICE.md.