I build File Viewer, an open-source browser-side file preview library.

github

Yu Wang  • Peerlist

Office preview looks easy until a customer uploads a real contract.The open-source File Viewer is great for broad, browser-side preview. It is not enough for every business file. Old DOC/XLS/PPT files, exact pagination, complicated tables, and huge spreadsheets can turn a clean demo into a terrible production bug.Flyfish Office Preview is the commercial path for those cases. It embeds DOC, DOCX, PPT, PPTX, XLS, and XLSX preview in SaaS products, OA systems, knowledge bases, contract tools, archives, and private intranets.Teams get complete source delivery, commercial or enterprise licensing, private deployment guidance, integration support, and one year of version updates on the commercial plan.The product is already used in telecom, university, and industrial-internet work shown on the product page.Demo: <a target="_blank" rel="noopener noreferrer nofollow ugc" class="break-all link-break text-gray-500 hover:underline" href="https://demo.flyfish.group/">https://demo.flyfish.group/</a>We do not claim perfect fidelity. We built this for the point where a general open-source renderer is no longer good enough and the release needs a clear owner.

Flyfish Office Preview

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?