Web Archive Viewer is a Firefox add-on designed to facilitate access to cached versions of websites. It employs seven different engines to render archived content, allowing users to select from three default engines or customize their selection via the options page. This flexibility ensures that users can choose the best engine for their needs, enhancing their browsing experience.

The add-on features a straightforward toolbar popup UI that enables users to easily switch between different archive engines with a simple click. However, it is important to note that not all websites have cached versions available, and the appearance of the cached content may vary depending on the selected engine. This tool is ideal for users seeking to view past versions of web pages quickly and efficiently.