Peek is a browser extension that shows previews for links to files and supported services in web pages. Just hover your mouse over a link, and Peek will display a small popup with an interactive preview of the link's content. Peek can show previews for PDFs, Microsoft Office documents, YouTube video links, audio files, Google Docs, and much more. It uses the browser's built-in rendering features, in combination with the Google Docs Viewer, Microsoft Office Web Viewer, and other third-party embedded viewers to display rich previews. Peek is open source under the GPL license. The code is available on GitHub: https://github.com/corbindavenport/peek