@@@ File

What are @@@ files and how to open them

Are you having problems opening a @@@ file or are you simply curious about its contents? We're here to explain the properties of these files and provide you with software that can open or handle your @@@ files.

What is a @@@ file?

A .@@@ file is a DOS 2.0-3.2 Backup Control Info file.

DOS 2.0-3.2 Backup Control Info files (with the .@@@ extension) are small metadata files produced by the BACKUP utility in MS-DOS versions 2.0 through 3.2 and by FreeDOS when using its "old format" (/v switch for version ≤ 3.2). The primary purpose of a .@@@ file is to identify a floppy (or backup medium) as part of a DOS backup set and record which disk it is, when it was made, and whether it's the only disk or the final disk in a multi-disk backup. On your computer one might see a file named BACKUPID.@@@ alongside backed-up files.

These files are written automatically during a backup session by the BACKUP program. They are never the full backups themselves; you use the corresponding RESTORE program with the backup medium and its .@@@ control file to restore files. In FreeDOS or MS-DOS 2.0-3.2 style backups, each disk in a multi-disk set has its own control file; if only one disk was used or it is the last disk, the control file marks that accordingly.

Control files are 128 bytes long. At offset 0 a byte indicates if this disk is the only or last disk (0xFF) or not (0x00). At offset 1 a 2-byte word gives the disk's sequence number. At offset 3 a 2-byte word records the year of creation. At offsets 5 and 6 single bytes record the day and month. The remainder of the file (from offset 7 through offset 127) is all zeroes.

How to open @@@ files

Important: Different programs may use files with the @@@ file extension for different purposes, so unless you are sure which format your @@@ file is, you may need to try a few different programs.

While we have not verified the app ourselves yet, our users have suggested a single @@@ opener which you will find listed below.

Last updated: August 14, 2026

Various apps that use files with this extension

These apps are known to open certain types of @@@ files. Remember, different programs may use @@@ files for different purposes, so you may need to try out a few of them to be able to open your specific file.

Help us help others

File.org helps thousands of users every day, and we would love to hear from you if you have additional information about @@@ file formats, example files, or compatible programs. Please use the links below or email us at submit@file.org to discuss further.