GitHub Office Preview

About

GitHub Office Preview adds a one-click Preview button to .docx, .xlsx, and .pptx file pages on GitHub, replacing the "Sorry, this file's contents could not be rendered" fallback with an actual rendered view. No downloading, no desktop app, no leaving your browser.

Why this exists

AI tools now generate a lot of Office output too, reports, spreadsheets, decks. Checking one currently means downloading it and opening Word, Excel, or PowerPoint. This previews it right where it already lives.

How it works

Open a .docx, .xlsx, or .pptx file on GitHub and click Preview.

Word documents render as formatted pages, including text, tables, images, brand cover backgrounds, and banners.

Excel workbooks render as plain data tables with a tab per sheet, values only. Formulas are shown as their last-saved result, not live recalculated.

PowerPoint decks render as a scrollable list of slides fitted to the page, including shapes, text, images, tables, and charts.

Every rendered preview carries a small notice that this is an approximate rendering, not a pixel-perfect copy of the original application.

Rendered by our own engine, not Word or Google Docs

There's no Microsoft or Google anywhere in the loop. The preview is drawn entirely in your browser by a renderer we built on top of open-source parsers (docx-preview, SheetJS, and pptx-renderer), with a stack of our own fidelity patches and a custom page-layout engine on top.

Honestly, matching how Word lays out a page turned out to be hard: brand cover art, rotated accent shapes, page breaks, headers and footers, cropped images, hanging indents. We chased each of those down against real documents, one rendering round at a time.

It won't be pixel-perfect. A browser's font metrics aren't Word's layout engine. But it does its earnest best, and it never asks you to leave the page or trust a third party with your file.

If something looks a little off, that's the renderer working hard, not your document.

Built for privacy from the ground up

No sign-in, no account, no API token, no server of any kind.

Everything happens locally in your browser. The file's raw bytes are fetched once from GitHub itself (the same file you were already looking at, via a plain same-origin request) and parsed entirely client-side by bundled open-source libraries. Nothing is uploaded anywhere, and no third party ever sees the file's contents.

This ruled out the two most obvious alternatives: Google Docs Viewer and Microsoft's Office Online Viewer. Both require sending the file to their own servers, and neither can be given a private repository's contents at all.

Works with private repositories too. Anything you can already view on github.com, you can preview.

Two permissions are worth knowing about, and they're both small:

storage remembers your two settings: auto-preview, and the size threshold below which auto-preview renders immediately.
Host access is limited to https://github.com/, using the standard content-script match every version of this extension has had. It is used only to detect Office file pages and fetch the file you're already viewing.

A size limit protects your tab, not your privacy. Parsing a large spreadsheet or deck client-side takes real time, so files over an adjustable threshold (5 MB by default) show a "click to render" prompt under auto-preview instead of parsing immediately.

A manual click always renders regardless of size. That click is your call either way.

Why we're proud of this one

This is our first extension, and getting it onto both the Microsoft Edge and Chrome stores is a milestone for us.

It looks simple, a button that shows you a document. But doing that faithfully, entirely in the browser, with nothing uploaded anywhere, took real work and a lot of learning.

We shipped it in the open, one honest fix at a time, and we're glad it's out where anyone can use it.

Built by https://bauerautomate.com