File Extensions

Section 1.2 File Extensions

There are many different types of files. At the very basics, we have images, videos, documents, and songs, but there are so many more. Even within each of those categories, there are numerous types. You may be familiar with a PDF and a Word Document. Both of those could be classified as “documents”, but are interacted with very differently. Whether you are an advanced computer programmer or someone who uses a computer for every-day purposes, an understanding of file extensions is essential. File extensions help us understand what type of file we are working with and give us an idea of how we can interact with that file. The following chunks give common (and some not so common) extensions for various categories. Refer back to this section often, especially if you find yourself forgetting what a file is.

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Hint: Control + F or Command + F work well on this page.

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Subsection 1.2.1 Images

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Why would we need more than on extension for an image? A photo is a photo, right? Wrong. Each of the file extensions have unique aspects and features. For instance, the Apple .heic file often takes up less storage space. However, not all programs can open them. The University of Michigan ¹⁹ and Kinsta ²⁰ have great guides on the differences between some image file extensions. The table here just lists the extensions and what they are, not the details on their use.

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Table 1.2.1.1. Image File Extensions

Extension	File Type
`.jpg` or `.jpeg`	Joint Photographic Experts Groups image
`.png`	Portable Network Graphics image
`.svg`	Scalable Vector Graphics image
`.gif`	A looped image/video blend
`.eps`	Encapsulated PostScript (vector) image
`.bmp`	Bitmap image
`.tif` or `.tiff`	Tagged Image File Format
`.raw`	Raw image (usually from a camera)
`.HEIF`	High Efficiency Image File
`.HEIC`	High Efficiency Image Container (Apple)
`.psd`	Adobe Photoshop
`.ai`	Adobe Illustrator

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Subsection 1.2.2 Videos

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Adobe ²¹ has a great guide on the differences between some video file extensions. The table here just lists the extensions and what they are, not the details on their use.

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Table 1.2.2.1. Video File Extensions

Extension	File Type
`.mp4`	MPEG-4
`.mov`	QuickTime Movie
`.wmv`	Windows Media Viewer
`.avi`	Audio Video Interleave
`.prproj`	Adobe Premiere Pro Project
`.aep`	Adobe After Effect Project
`.fcp`	Apple Final Cut Project
`.camproj`	Camtasia Project
`.m4v`	iTunes Movie File

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Subsection 1.2.3 Documents

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There are many different file extensions that refer to documents. Many of them you will never encounter. Only the main file types are listed here. File Stack ²² has a good explanation on some of the file types here.

Extension	File Type
`.doc` or `.docx`	Microsoft Word Document
`.xsl` or `.xslx`	Microsoft Excel Spreadsheet
`.ppt` or `.pptx`	Microsoft PowerPoint Presentation
`.pages`	Apple Document
`.key`	Apple Keynote Presentation
`.numbers`	Apple Numbers Spreadsheet
`.pdf`	Adobe Portable Document Format
`.rtf`	Rich Text Format Document
`.txt`	Plain Text Document
`.log`	Text Log File (often records messages)
`.md`	MarkDown Document
`.Rmd`	MarkDown Document for use in R

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Note: technically, .html and .xml are considered document-type files. I am choosing to place them under coding-type files instead.

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Subsection 1.2.4 Audio

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makeuseof.com ²³ has great descriptions of the most common audio file types.

Extension	File Type
`.mp3`	MPEG Layer 3 (lossy compression)
`.wav`	Waveform Audio Format (uncompressed)
`.aiff`	Audio Interchange File Format (uncompressed)
`.aac`	Advanced Audio Coding (lossy compression)
`.wma`	Windows Media Audio (lossy compression)
`.flac`	Free Lossless Audio Codec (lossless compression)
`.aa` or `.aax`	Audible Audio File
`.m4a`	Audio-Only MPEG-4 (iTunes)
`.midi`	MIDI File

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Subsection 1.2.5 Coding and Programming

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There is a plethora of programming languages, software, and interfaces and each of them uses a different file extension.

Extension	File Type
`.R`	R Script
`.py`	Python Script
`.ipynb`	Jupyter Notebook
`.html`	HyperText Markup Language
`.css`	Cascading Style Sheets
`.js`	Javascript
`.sas`	SAS Script
`.xml`	eXtensible Markup Language
`.xslt`	eXtensible Style Sheet Transformations
`.ptx`	PreTeXt Markup File
`.tex`	LaTeX Document (typically for mathematics)
`.c`	C and C++ File
`.cpp`	C++ File
`.java`	Java Source
`.swift`	Swift Code File
`.vb`	Visual Basic File
`.vbs`	Visual Basic Script

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Subsection 1.2.6 Data

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Many of these extensions also belong in Subsection 1.2.3 but are related enough to merit another subsection.

Extension	File Type
`.csv`	Comma Separated Values
`.tsv` or `.tab`	Tab Separated Values
`.json`	JavaScript Object Notation
`.csv`	Comma Separated Values
`.tsv`	Tab Separated Values
`.rds`	Single R Object
`.RData`	Multiple R Objects
`.sas7bdat`	SAS Data File

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Subsection 1.2.7 Other File Exensions

Extension	File Type
`.band`	Apple GarageBand File
`.logicx`	Apple Logic Pro File
`.exe`	Windows Executable File
`.zip`	Compressed Files
`.tar.gz`	Collection of (archived) files
`.app`	Mac Application
`.dmg`	Mac Disc Image (executable file)
`.pkg`	Package of Software or Files
`.otf`	Open Type Font
`.ttf`	TrueType Font

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