A Straightforward Guide to File Slack


File slack is an extremely complex issue that requires a bit of studying to grasp. Fortunately, this article simplifies the concept for even the least technical users to understand.

What Is File Slack?

File Slack, also called ‘slack space’, is the leftover space on a drive where a file is stored. This space remains empty or left over because each cluster on a disk has a storage threshold and files are random sizes. Therefore, the files only fill a part of the hard drive portion.

Imagine you have a bowl and lid. In this example, the bowl is a portion of a computer hard drive. Next to the bowl is a cup of pudding, in this case it is the file. You pour the pudding into the bowl, it fills the bowl about three-fourths, then you seal it. Note that the pudding hasn’t completely filled the bowl. The remaining space between the pudding and the lid is the file slack. When a file is saved, the computer puts it into a hard drive cluster on the hard drive (bowl), and it has some leftover space.

A man is adjusting the hardware components of a partially disassembled laptop on a table in front of him.
There is extra space around a saved file.

How File Slack Is Utilized

File slack is a result of computer functionality and there are unintentional benefits of this semi-flaw. The most prevalent benefit occurs in the computer forensics field, as file slack allows users to locate files deleted from sectors. Deleting computer files doesn’t fully delete them – it just moves them. This provides investigators potential clues as to the data erased by legal suspects on the hard drive.

Computer forensics solves notorious criminal cases by utilizing file slack data to find missing information or clues. One of the most recent, high-profile cases was in the investigation of American Secretary of State Hillary Clinton and deleted emails. The investigators explained the task of retrieving data because of the extra space in deleted files.

A female computer technician is inspecting a printed circuit board with some processor chips with the help of a magnifying glass.
Computer forensics can recover deleted data.

Further Considerations

File slack is a reminder that it’s hard to erase something permanently from computers. Evaluate sensitive information often to determine whether it’s something important enough to keep off digital mediums. From basic things like a secret recipe for an award-winning stew, or more complex issues like business data, understanding slack space keeps companies protected.

Though file slack remains a rarely mentioned term, it resurfaces every now and then. Understanding its uses and possibilities keeps you ahead of the average user, researcher or business.