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File Extensions 101

When it’s time to save your work and step away from the computer for the day, choosing the right file extension is just as important as the long hours you put into your project. Whether you have been working in Adobe Photoshop, Illustrator, InDesign or any other program, the physical act of choosing a file extension is elementary. But, choosing the correct extension can be the difference between life and death for your document.

A file extension is the suffix at the end of every document on your computer, such as the “.doc” seen at the end of Microsoft Word documents. File extensions are unsung heroes. When a file has the correct extension, you never really notice that it is properly preserving a project. Giving a document the wrong extension, however typically results in fits of rage. A document with the wrong file extension may alter the properties of a document, rendering it useless for your needs. It is a simple mistake, but trust us, you want to take a minute to choose the right file extension.

Remember: save early, save often and save correctly.

While there similarities among extensions, no two file extensions are alike. We created a breakdown of the file extensions most commonly used by graphic designers to help make sure you save your documents without worry.

.AI

This is Adobe Illustrator’s proprietary extension. Because .ai files are vector based, you can enlarge or shrink the image size without worrying about pixelation. Graphics created in Illustrator typically have multiple layers. The .ai file extension preserves layers, whereas some other file types may flatten the document into a single layer. Working with .ai files also comes with the added benefit of easily importing into other Adobe Creative Suite programs like Photoshop or InDesign.

.BMP

Known as “bitmap image file,” .bmp files are raster graphics, which look fine when scaled down in size, but become pixilated when enlarged. The nice thing about .bmp files is that they have a better image quality than other raster file types such as .jpg or .gif files. The bad thing is that the files are typically larger than raster files, making .bmp an unlikely choice for Web graphics, but a good option for print documents.

.EPS

This file type can be opened in virtually any graphic design program (including Photoshop, InDesign and Illustrator), making .eps highly popular amongst graphic designers. This is a vector-based file type, and like .ai files, .eps files will keep layers and other complex information intact after saving.

.GIF

In most cases, high-quality images are your best bet. But, when it comes to websites, smaller data files means faster load times. This is the reason why .gif files are perfect for the Web. Many websites use .gif images because they are compressed files that are smaller than other raster graphics. Also, these files support animations, which can add nice flavor to a website. However, .gif files shouldn’t be used for high-quality images.

.INDD

This is the proprietary Adobe InDesign file extension; used for creating layouts for books, magazines, newspapers and other media. An .indd file can’t be opened by other Adobe programs. However, many file types can be opened within InDesign to create appealing layouts.

.JPG

The .jpg, or JPEG file extension is a raster file type. The image quality degrades if you try to enlarge the size of a .jpg. Also, the image quality of .jpg files are like a Russian nesting doll. Basically, a JPEG will lose image quality each time changes are made and saved. But, there are two benefits to this file type. JPEGs are smaller files that have a higher capacity for image quality than .gif files. In fact, many of the high-end Web graphics you see are probably JPEGs.

.PDF

This file type is the most straightforward of the bunch. For the most part, a .pdf file is not meant to be edited. It’s meant to be kept intact, exactly as it is saved. If you are completely finished with a document, this file type will make sure your viewers see the document exactly as it was created no matter where they view it, be it on the Web or in print.

.PNG

Like JPEGs, the .png file supports high-resolution images, but won’t lose its image quality after too many saves. A bonus to using this file type on websites is that it has “transparency” properties. This allows .png files to be placed any color background without worrying about a nasty “ring” effect around the border. The downside to .png files are that they are larger files than JPEGs and they don’t support animations like .gif files.

.PSD

This is the file extension for Photoshop files. While it is a raster file like .jpg and .gif files, it has some important differences. The biggest difference is that the a .psd file maintains layers and other high-level data, whereas a .jpg file flattens and compresses data to create a smaller file size. Like .ai files, a .psd file can be easily imported into other Adobe programs such as Illustrator or InDesign.

.TIFF

The .tiff file is one of the least used file extensions on this list. It is typically a large file size, and it won’t compress data after being saved. Besides not compressing, the biggest benefit to .tiff is that these files can be opened and viewed by every major operating system, making it a viable choice for cross-platform raster graphics.

.ZIP

A “zipped” file is typically a batch of large files that are compressed and stored on a single .zip file. This is usually done to upload and download large files like logos. To retrieve the content from a zipped file, you need a program that can do this (which can be downloaded for free on the Web).