BOJ Extended is a Chrome add-on developed by L4zyF0x that enhances the BOJ Online Judge platform with additional features. This free add-on falls under the category of Browsers and the subcategory of Add-ons & Tools.

With BOJ Extended, users can enjoy various themes, including a dark theme, to customize their site experience. The add-on also offers a fullscreen mode that provides a wider view for a more immersive experience.

In terms of user profiles, BOJ Extended allows users to view problem numbers and titles, as well as compare solved problems with other users. Furthermore, users can display their solved.ac tier next to their nickname, adding a competitive element to the platform.

The add-on also simplifies access to group features, allowing users to quickly navigate through group rankings, problem sets, and other group-related content.

For those interested in checking their submission status and code, BOJ Extended provides a convenient interface to view problem numbers, titles, and submitted code. It also offers a brief explanation of runtime errors and allows users to customize the text of submission results through the "Options" page. Additionally, the add-on displays the latest judging status as a percentage.

Other notable features of BOJ Extended include a timer function for setting time limits on problems and quick search functionality using the "ctrl+/" or "alt+/" shortcut keys. Users can also customize the site's font to their preference.

Overall, BOJ Extended is a valuable add-on for users of the BOJ Online Judge platform, offering enhanced functionality and customization options to improve the user experience.