What is a duplicate file?
Last update: September 8, 2025
In computing, a duplicate refers to a file that appears multiple times with identical content. Except for backup copies, duplicates are generally viewed negatively.
In this article, we will look at the importance of distinguishing between the two categories of duplicates that can occur: identical duplicates and similar duplicates.In this article, we will look at the importance of distinguishing between the two categories of duplicates that can occur: identical duplicates and similar duplicates.
Are all duplicates the same?
The question may sound amusing, but it is important. We need to distinguish between two types of duplicates: those that are identical and those that are similar.
“Identical duplicates are just a specific case of similar duplicates.”
Identical duplicates:
This category includes files that are strictly equal at the binary level. They have the same size and perfectly identical content. This type of duplicate can easily appear, for example, when simply copying and pasting a file.
Writing software to identify identical duplicates is relatively simple. A comparison of file sizes is already enough to determine if they differ, an operation anyone can perform with a file explorer. This simplicity explains why there are so many, mostly free, programs capable of effectively removing these duplicates.
Similar duplicates:
Some files are not strictly identical but show perceptual similarities. This is especially true of multimedia files such as photos, videos, or audio recordings. A similar duplicate may appear after a slight image edit, a conversion to another format, or a different compression.
To the naked eye, the files may look identical, but their content is stored on the disk in a completely different way. This is why classic duplicate finders that detect identical files turn out to be ineffective: they cannot perform perceptual analysis, which is far more complex.
Why is this distinction important?
Because it is precisely the similar duplicates that represent, in most cases, the most common category and the one that takes up the most storage space. They are therefore the ones that should be targeted first.
“Similar duplicates make up the majority of duplicates on a storage device.”
Deleting only identical duplicates generally frees up very little disk space.
Only a handful of programs can perform an in-depth analysis of multimedia files. Duplicate Media Finder is one of them. This software can analyze all types of files (images, videos, music), quickly and easily, while offering very useful advanced features.