File Extensions Guide: Full Forms, Uses & Examples

What is a file extension?

A file extension is the short group of letters after the last dot in a file name. In photo.jpg the extension is .jpg. It tells the operating system which program should open the file and what kind of data is stored inside. Without it your computer would not know whether a file is a picture, a song or a document.

Why should students learn file extensions?

Online forms often ask for a photo in JPG under 50 KB, a signature in PNG or a scanned certificate in PDF. Choosing the wrong type is one of the most common reasons an upload fails. Knowing the difference between lossy and lossless images, between documents and archives, and between audio and video helps you finish online admissions, exams and job applications without stress.

Main categories

Image files (PNG, JPG, GIF, WEBP, SVG), document files (PDF, DOCX, XLSX, PPTX, TXT), audio and video files (MP3, WAV, MP4, MKV, AVI), archives (ZIP, RAR), web files (HTML, CSS, JS, JSON), data files (CSV) and system files (EXE, APK, ISO). Each has its own page here with the full form, meaning, uses, examples and the best software to open it.

Complete list at a glance