How and When to Use Different Image Formats

When you download a picture, animated graphics, logo or other image files to your computer, it takes a specific file format. While you can often convert these initial file formats into a different type, doing so is not always a good idea. Let’s explore the most common image file formats used in web design and take a look at what each one is intended to do.

Why Image File Formats Matter

It’s easy to think that all file formats are created equal; after all, most of them will get an image onto your hard drive or rendered on a webpage. However, the specific image format you choose does matter quite a bit when it comes to quality performance. Take a look at this image as an example.

PNG vs. JPEG

Look at the fox’s eyes in the example on the left, then look at the example on the right. Look at the color difference and the way the lines around the perimeter of the graphic render. As you can see, there are sharpness and clarity issues in the JPEG graphic that aren’t present in the PNG. The PNG is sharper, clearer and more professional looking. That’s because it is specifically designed to handle computer-generated graphics like the one in the example. Which graphic would you want on your site? If you want to stand out in the right ways, you’ll choose PNG for computer-generated graphics.

You can see the difference between file sizes for different formats of the same image in the graphic below.

Image performance and file size

Ultimately, the different file formats serve specific purposes. They render the same graphics and images in different ways and carry different file sizes. Knowing what each one is for and when to use them is the key to proper design rendering and performance in the digital space.

When to Use JPEG Files

JPEG is the ideal file format for photos, though it’s not a good format to use for computer-generated graphics. It’s currently the most common image format found in the digital space, and it’s easy to store and send, making it convenient for a variety of different design scenarios.

Pros:

  • Small file size
  • Excellent compression with constantly evolving improvements
  • Widely supported across different browsers and applications
  • Ideal for storing crisp, clear photographs
  • Fast loading through HTTP/2

Cons:

  • “Lossy” compression creates diminishing return on image quality as compression rate rises
  • Not to be used for computer-generated images
  • No transparency for design

When to use PNG files

You should always use PNG files when you’re working with computer-generated images such as logos. With this file format, the more complex the image is, the larger the file size becomes. Because of this, even though you theoretically can use this image format for photographs, the .PNG is best for vector graphics and other computer-generated image files.

PNG-24 vs. 8

When you’re using PNG files, you may notice that there’s two kinds: PNG-24 and 8. PNG-24 offers crisper image quality with better transparency than PNG-8, but it comes at a price. The image size for PNG-24 files can be much larger than PNG-8 files, and that means download time can be slower. However, PNG-8 does serve its purpose well when transparency is not an issue.

PNG Pros

  • Widespread compatibility across different browsers and applications
  • Can be made transparent to layer over other images in a design
  • High image quality

PNG Cons

  • File size can be large and cumbersome
PNG 24 vs. PNG 8

When to Use SVG Files

Standard vector graphic (SVG) files are the for computer-generated vector images. That means logos, digital drawings, patterns, and icons, among others. This image format represents the cutting edge of web design technology. However, when using SVG files, designers often provide a PNG fallback as well to allow for outdated browsers that do not yet work with them.

SVG Pros

  • Small file size
  • Ideal for all computer-generated graphics
  • Easily formattable with code CSS, HTML or Javascript

SVG Cons

  • May not be compatible with all browsers. See the browser support here.
  • Doesn’t support complex images with lots of depth and color, including photographs

When to Use GIF Files

In common internet parlance, GIF refers to an animated image that runs on a loop and has no sound. These animated images and memes are pretty much the only useful purpose the GIF serves at this point. The .GIF file extension is not ideal for photos or complex illustrations.

Cloud war animation

Animation by Chris Philips

GIF Pros

  • Small file size
  • Reliable site performance
  • Can support looping animation

GIF Cons

  • Low resolution capacity
  • Poor image quality
  • Unnecessary given the availability of superior image file formats

How to Choose the Right Image File Format?

When it comes to choosing the correct image file format, the best first step is to determine what kind of image you have and go from there. If it’s a photograph, use JPEG. If it’s a company logo or illustration, use PNG. For icons and logos, you can also use SVG. If it’s an animated image, use GIF.

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