The bookmarks stored in Opera internet browser are saved with the extension ADR. This bookmark file saves the website address of webpage which is bookmarked by the user.
Along with this the bitmap image which is often the logo of the website is also saved within the file. When the user opens bookmark folder from Opera the bitmap image is used as icon to display the bookmark. Other elements which are included in ADR file format include the title of webpage and other elements which are added by the user including description of the bookmark, tags and comments. Each webpage bookmarked is saved with separate ADR file.
In addition to the problem described above, i.e. the lack of the appropriate application to support the .ADR file, there may be several reasons that cause problems with opening and operation of the data format:
A quite common problem is the lack of application in the appropriate version. Even if you have an application, with the help of which you should open the .ADR file, you may have a problem with it because of its version. Perhaps in previous versions the application has not yet supported the .ADR file, so download the update and check again.
If you have already installed the appropriate application, and it is the correct version, the file may not open correctly, because the operating system does not have information that this program supports the file. So you need to "show" which program the computer should use. To do this:
It also happens that the file you want to open is corrupt and therefore there is no such possibility. In this situation, you should find its different version, or ask a person from whom you got, to send it again.