Uploading a private DOCX just to preview it is awful.
File Viewer keeps the file in the browser. Its format catalog registers 275 extensions across 47 preview pipelines, including Office, PDF/OFD, CAD, archives, email, diagrams, ebooks, media, 3D and data. Of these extensions, 225 are marked stable and 50 experimental; actual availability depends on the renderers installed.
Use it with plain JavaScript, Web Components, React, Vue, Svelte or jQuery. Workers, WASM, fonts and other assets can stay on your own server, so private and offline deployments do not need a public CDN.
The ugly parts are still real. Complex Office files can lose fidelity, and huge files can eat memory or crash a tab. This is a preview tool, not Microsoft Office rebuilt in JavaScript.
