Uploading a private DOCX just to preview it is awful. File Viewer keeps the work in the browser. It maps 206 extensions to 24 lazy preview pipelines for Office, PDF/OFD, CAD, archives, email, diagrams, 3D, media and data. Use it with plain JavaScript, Web Components, React, Vue, Svelte or jQuery. Workers, WASM, fonts and other assets can stay on your own server. It is Apache-2.0. Office fidelity and huge files are still the hard parts.