What Are File Extensions?

Code on the screen

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Thanks to advances in technology, our desktop computers, laptops, tablets, and smartphones are capable of more than ever before. We have various different pieces of software (or computer programmes) that we can use in order to complete various different tasks. We can type up documents, make image files, upload photographs and so so much more. But have you ever wondered how different programmes save their files? Computer files have specific characteristics that depend entirely on the programme that you used to create them. This is why sometimes you need the same software that someone made a document in to be able to view it if they send it to you. Either that, or people have to convert file types in order to make the document accessible to you on your computer. The easiest way to go about this is to understand files and file extensions. A surprising number of people don’t understand this and life can easily become difficult for them when they’re trying to navigate their way through various types of documents. But the good news is that with a little research and effort, you can come to understand this seemingly complex information relatively easily. We just have to strip away the jargon and be straightforward about things! So, this is where we can come in to your aid. Here’s absolutely everything that you could possibly need to know about files and file extensions!

What Are File Extensions?

File extensions are the last part of a file name. In the early days of computer development, file extensions weren’t exactly extensive. They could only contain up to seven different letters. But since 1995, developers have been able to incorporate a full stop into file names and nowadays you can generally make a file name as long as you like and this will simply be followed by a file extension which usually starts with a full stop and is followed by a few (usually three) letters that indicate the file type. Now, file extensions are extremely useful as they help you to easily identify the type of file that you have created or received before opening it. This can save you time and hassle, as if you try to open the wrong type of file in a programme, the programme can crash. If you are opening the file when you don’t already have any programmes open, by clicking the link that you have been sent, the file extension allows your computer to automatically know the right programme to try to open it with, or can suggest that you download the correct programme in order to engage with the file. Now, this is a very basic explanation and there is, of course, a whole lot more that can go into this. If you want, you can find out more at File-Extensions.org. For now, let’s focus on a few of the most common and popular file extensions out there!

.doc and .docx

Files ending in the extensions .doc and .docx belong to Microsoft Word. This is the one of the most popular pieces of word processing software on the market, so chances are that you’ve either used it to create and save documents in the past, or have received a word document at some point or another. Doc files generally contain plain text, but they can also contain images, graphs, tables, and various other types of information. So, what’s the difference between .doc and .docx. Well, .doc is the original file extension used by Microsoft Word that allows documents to be opened in this software only. Other word processing programmes can have difficulty opening .doc documents. This is why .docx was developed. .docx allows other word processors to view documents created in Microsoft Word, as the behind the scene coding work has been carried out in XML (hence the “x” in the .docx file extension).


Many people may not find differentiating between a Microsoft Word document and a PDF all too simple. The easiest way to spot the difference is to take a look at the file extension. If the file ends with .pdf, it’s a PDF. It really is as simple as that! But a PDF (short for “portable document format files”) is actually something completely different to a word document. In fact, a PDF is a file format that is used for capturing and sending electronic documents in exactly the format that is intended. So the reason that we often associate PDFs with word documents is because we tend to send more word documents than any other form of document so most PDFs that we send and receive mirror the typical word document’s format. This file type is primarily used for viewing, not editing.


.jpg is the file extension most often associated with image files. It is actually a file extension for lossy graphics files. If you see JPEG, don’t worry, this is just an interchangeable file type with JPG that is more often used for photographs downloaded onto your computer device rather than graphics and images created in programmes on your computer itself. This file type can be opened by most image viewing software and also image editing software such as MS Paint and Photoshop. This is the most popular file type, as it compresses the image, making it easier to share, store, and also to display on websites. However, if you are working with high-quality images and want to maintain the original image quality, it may not be the ideal option, as the compression also reduces file quality. This isn’t something that will make much difference for a standard computer user and only something that might concern professionals working with smaller details of the image.

Filename extensions were originally used to easily determine the file’s generic type and the necessity to condense a file’s type into three characters frequently led to abbreviated extensions. Examples include using .GFX for graphics files, .TXT for plain text, and .MUS for music. However, because many different software programs have been made that all handle these data types (and others) in a variety of ways, filename extensions started to become closely associated with certain products—even specific product versions.But hopefully we’ve helped to clear up any concerns that you might have initially had. These are only three file types that we’ve covered, but they are the most commonly and widely used ones out there, so are definitely three that you should get to grips with as soon as possible!

Just a regular computer user. I write for regular users like me. When we grow up we are taught basic security tips like how to cross the street. But we are not taught how to take care of ourselves online.