A Guide to When and How to Use Them
Other than government agencies and the text messages of your common variety pre-teen, there is no great collection of two and three-letter acronyms than the myriad file extensions that we encounter in our digital world daily.
Some, like .doc, are so ubiquitous that unless you’re Amish, or you’ve been in a coma for the last 25 years, you know exactly what they are. But others, like .webm or .s7z, are more esoteric and require advanced degrees in the dark arts to become privy to their shrouded secrets and hidden purposes.
Lucky for you we hold multiple black belts in file format designation and can help clear up some of the confusion. No longer will you need to feel stupid when the chatter around the water cooler inevitably circles back to .tif files and their relative merits compared to a standard .tga. After perusing this guide, you’ll be a file format phenomenon, which, if you were a digital file, would be a .ffp. We’re going to focus on the more common file types for this guide. It’s unlikely that most people will encounter .?XF files in their lifetime, and if someone you know does send you these compressed files for the QNX4 operating system, you’re probably the sort of person that knows what they are.
Without further delay, let’s dive in!
Image File Types
Still images come in a wide variety of formats, many of which are used for specialized applications that most of us will never see. These are some of the most common.
JPEG: .jpg – Joint Photographic Experts Group
This is one of the most common formats on the web. JPEGs are lossy, compressed images, which means their file sizes are significantly smaller than other formats. This is good for the web, but the more the file is compressed, the lower the image quality. It’s best to compress only as much as is needed to deliver the required file size.
GIF: .gif – Graphics Interchange Format
GIFs used to be extremely common in the early days of the web. Today we know them mostly from the funny motion GIFs we send to each other and post on social media. GIFs are very small files because they’re limited to 256 colors or less. This was good for the web but not much else, which is why you don’t see them much anymore.
PNG: .png – Portable Network Graphics
PNGs took over where GIFs left off. PNGs are a lossless format, which means they can be edited without losing resolution but at a similar scale are larger files than JPEGs. PNGs are the best choice for applications where a transparent background is required, like a logo that needs clean edges instead of being surrounded by a white box.
EPS: .eps – Encapsulated Postscript
This is the leading generic vector graphic format. Unlike the first three image types on this list, which are bitmapped, vector graphics aren’t based on pixels. They’re based in math, which means they can scale cleanly to any size and resolution. These are commonly used for applications where artwork needs to fit many different formats. Logos are a good example.
A more proprietary format for vector graphics is the .ai, or Adobe Illustrator format.
Camera Raw: .raw, .nef and Many Others
These images are the raw, unprocessed data that’s captured by a digital camera’s sensor chip. They are very large files as a result. They aren’t intended for use by the end-user but instead are used by photographers to get clean image manipulation and color manipulation. Once a photographer has finished editing his or her photos, they would get saved in a more user-friendly format, like a high-res (minimally compressed) JPEG.
Video File Types
As with still images, there is an enormous number of video formats. Many are tied to particular cameras and don’t make their way into consumer’s hands. Below are some of the more common formats you’re likely to find.
MOV: .mov – Apple Quicktime Movie
Quicktime is Apple’s video playback engine for its Mac computers. The MOV format was created as their generic video container format. Several different codecs, or methods for compressing video, can be used to encode a MOV, but the file extension remains .mov. MOVs are still commonly used when editing video on a Mac, but they’ve fallen out of favor as a final delivery format.
MPEG4: .mp4 – Moving Pictures Expert Group 4
The MPEG4 has replaced MOVs as the most common video delivery format. It features clean compression and high-quality video playback. Many consumer video cameras will shoot natively in the MPEG4 format. The format was created in 1998 by the industry group that gave the format its name as a standard web video format.
If MPEG sounds familiar to you, that’s because there have been many revisions over the years. MPEG2 was the video format used for encoding video DVDs.
AVI: .avi – Audio Video Interleave
This is one of the oldest digital video formats, having been introduced in 1992 as the generic video container format for Windows machines. Like MOVs, AVIs support several different video and audio codecs. AVIs have fallen out of favor in recent years, although AVIs using the DivX codec are still used in some circles.
WMV: .wmv – Windows Media Video
Microsoft created WMVs as a streaming format for the early web. They feature some of the smallest file sizes available for video, which makes them one of the few, if not the only video format that can be sent through email. However, this portability comes at a cost. WMV image quality is generally very bad.
Audio File Types
The world of digital audio is dominated by one particular file type, the MP3, but it’s by no means the only player in the field.
MP3: .mp3 – MPEG-1 Audio Layer 3
It’s hard to believe, but the humble MP3 was created back in 1993, and it’s still the dominant audio file format today. MP3s feature lossy compression, which means audio information is lost the more compression is applied to the file. That’s why highly compressed MP3s sound tinny and lack definition.
However, it’s this lossy compression that allowed the files to take root when they were created. Back when digital audio players didn’t have a lot of hard disk space, you needed tiny audio files. Today MP3s are still used, although they tend to be compressed very little, to maintain sound quality.
WAV: .wav – Waveform Audio File Format
WAV files are slightly older than MP3s but aren’t quite as well known because they weren’t intended for mass audiences the way MP3s were. WAVs are an audio container, which means they can hold different audio codecs, though most commonly use the PCM or pulse-code modulation codec, which is an uncompressed codec. This means WAV files are big, but the audio quality is very high.
AIFF: .aif – Audio Interchange File Format
WAV files were created for PCs. Apple created AIFFs for Macs. They’re both audio container formats, and both generally use the PCM codec, which means, other than the name and a few minor differences under the hood, WAVs and AIFs are almost interchangeable.
FLAC: .flac – Free Lossless Audio Codec
FLACs, while not nearly as common as MP3s, are worth mentioning because they represent a different type of compression. The feature lossless compression, which shrinks an audio file’s size without throwing away information. Depending on the source, FLACs can reduce file size by 60% without compromising audio quality. Nearly all digital audio players support FLACs. Now that digital audio players have large hard drives, it’s less important that FLACs can’t get as small as MP3s. Their superior audio makes the larger files sizes worthwhile.
We’ve Dipped Our Toe Into the Sea
We’ve covered some of the most common file types here, but there are so many more. Hopefully, this whets your appetite and clears up some of the confusion. If you’re interested in debating the relative merits of FLAC versus MP3, or the proper pronunciation of GIF (it’s JIF, as in the peanut butter), give us a call. We’re always happy to geek out on file extension questions.