Why are Most File Extensions Three Characters or Less?

This is one of the most commonly asked file extensions related questions. Before we dive into the technicalities involved in naming a file, let’s start with the basics.

What is a File Extension?

This is a name extension at the end of a file that helps us know the file type in an operating system like Windows/ Mac. For example, in Windows, most file extensions are made up of a period followed by three characters. But you might have one, two, or even four characters.

What Makes a File Extension Valid?

A valid file extension is often characterized by a period, two/ three/ four characters, and must come after a file name. For example, support.docx. Most of the latest OS versions hide file extensions by default. To view them you have to enable show file extension.

Now that we’ve gotten the basics out of the way, let’s get to the big question.

Why Three Characters File Extensions?

This is because many programs and file formats limit the extension to three characters. Moreover, not all operating systems supported extensions that were longer than three letters. MS-DOS, Windows 3.X, Windows 95,98, and NT, did not support extensions longer than three characters. Also, Microsoft Windows 2000, XP, ME, Vista 7 & 8 had a limit of three character file extensions. As a result, all programs running on these operating systems had to toe the line and work with the given guidelines. Hence the many three-character file extensions available today.

But can a file extension be longer than the three characters?

Today, most operating systems and programs have room for longer file extensions. All Apple operating systems, Linux, OS/2, BSD, and Unix allow you to have longer file extensions. Also, Microsoft Windows 10, 8, 7, and Vista have a 260 character limit for file names.

But for uniformity and to keep overall file name extensions short, most programs don’t go beyond the fourth character.

We hope this answers the question.