A REC file is a data recovery file created by fsck, a utility used to check the integrity of a file system in Unix and Unix-like operating systems. It contains a log of "inconsistencies" in a filesystem that were detected during an fsck check that can be analyzed by users to investigate issues in a file system. REC files are similar to .chk files created by the "CHKDSK" system tool for Windows.

The fsck tool is typically used in Unix-like operating systems, such as Linux, macOS, Free BSD. The utility typically runs during the bootup of the operating system to check the consistency of the filesystem. If the utility finds any issues, it logs them in one or more REC files to be analyzed. When fsck creates REC files it names them as FSCK####.REC with the #### ascending from 0000 for each data recovery file created. For example, the first REC file is FSCK0000.REC, the second is FSCK0001.REC, the third is FSCK0002.REC, and so on. REC files store data in plain text and can be opened with a text editor, such as Apple TextEdit or gedit. The files can also be deleted without affecting the performance of the system but they may be regenerated during the operating system bootup process. NOTE: fsck is short for File System Consistency Check.

A REC file contains video created by a Topfield PVR digital video recorder, a device used to record standard and high definition television programming. It is saved in a proprietary compressed format that can be viewed on a Topfield PVR device or with various third-party video players.

You will most likely only encounter a REC file if you own a Topfield PVR digital video recorder and have recorded TV programming. You may also receive a REC video file from someone who owns a Topfield PVR digital video recorder. REC files can be opened with various video players, including Squared 5 MPEG Streamclip and VideoLAN VLC media player. The VLC media player software can also be used to convert REC files to more widely supported video formats. NOTE: REC files are also known as Toppy files, since Toppy is short for Topfield.