A file with the Adr file extension is known as an Opera bookmarks file. The Adr file extension serves as a marker to your computer, enabling the file to be quickly located when needed by Opera.
On your computer, the Adr file is stored within the Opera program folder.
While browsing the Internet, you can save the location of a website using a bookmark. This list of bookmarks is contained in the Adr file, and when you want to visit the site again, you select it from the list that appears under the "Bookmark" menu.
To add a website to the Adr bookmark file, "Bookmark page" under the "Bookmark" menu. Alternately, you can press "Control" and "D" at the same time, and the site will automatically be entered.
The Adr file automatically updates when you add or delete a file on Opera, so you do not need to manually open the file on your own. Do not delete the Adr file as this could make Opera function improperly.