Uploading a private DOCX just to preview it is awful. File Viewer keeps the file in the browser.

It supports 206 file extensions through 24 preview pipelines: Office, PDF, CAD, archives, email, ebooks, images, audio, video, and more. Renderers load only when needed. Worker and WASM assets can stay on the same origin, so private and offline deployments don't need a public CDN.

The idea started in 2022 after I was asked to build an Office viewer with almost no server capacity. One library was never enough. I built a shared TypeScript core around separate format renderers, then added packages for Vanilla JS, Web Components, Vue, React, Svelte, and jQuery.

The limits are real. Complex Office files can lose fidelity. Huge files can eat memory and crash the tab. This is a preview tool, not Microsoft Office rebuilt in JavaScript.

Try the demo without an account. What breaks first in your app: fidelity, memory, browser support, or Worker paths?