Imposia Documentation

Imposia turns HTML and CSS into pages inside the browser. Preview and print use the completed pages; EPUB export uses the semantic source committed with them.

Choose where to start

• Build a working preview: follow Build your first page to install the React package and render HTML as A4 pages.
• Look up a component or method: use the API reference for React handles, Core controllers, Viewer navigation, reader controls, and lifecycle constraints.
• Understand the output: read How preview and output stay consistent before you connect printing, EPUB downloads, or external assets.

What happens to your HTML

1. Your app passes HTML, CSS, and page options to Imposia.
2. Core paginates the next version in a temporary iframe.
3. When pagination finishes, Imposia replaces the visible document in one step.

If pagination fails or a newer update arrives first, readers keep seeing the last completed document. They never see a half-finished layout.

Use one committed source in three ways

• Preview: show the completed pages through the React Viewer.
• Print: open the browser print dialog for those same pages.
• EPUB: create a reflowable EPUB 3.3 Blob from the document's committed semantic source.

Know the boundary

Imposia runs in the browser and ships as ESM. It does not include a Node renderer, a CLI renderer, a server publishing API, or a PDF generator. If that matches your application, continue with Build your first page.