The format you choose for images on your website affects appearance, file size and page load times. To design an attractive site with smooth functionality, it’s important to use the right format for each application.
JPEG, GIF and PNG are some of the most common image file extensions on the web. Each has advantages and drawbacks, and knowing which to choose can make a big difference in how your website looks to visitors.
An acronym for the Joint Photographic Experts Group, the creators of the format, JPEG is a 16-bit image style able to contain over 16 million colors. This diversity makes JPEG a good choice for photos and other images with complex colors and shading. A compression rate of 60 to 75 percent creates an image with an appearance similar to the original but with a smaller file size suitable for web use.
JPEG is best when you want cross-platform support for popular operating systems and imaging hardware. The reduced image size supports faster page loading, but this benefit comes at the expense of quality. To compress the image when saved, the JPEG format sacrifices some of the information it contains, hence why the format is called “lossy.” This process repeats each time the image is saved, resulting in compound degradation visible in the image.
Originally created to facilitate faster image transfers over slow Internet connections, the “graphics interchange format” uses 256 indexed colors and lossless compression to render much smaller image files than JPEG. However, even with this limited color selection, files can become cumbersome if too many colors are used in the same image. This makes GIF best for small web graphics, icons, buttons and navigation images. Since one color in a GIF can be transparent, these images may be placed anywhere without interrupting the visual flow of a webpage. GIFs can also be animated, a feature you can take advantage of to create eye-catching memes or moving graphics for social media.
Short for “portable network graphics,” the PNG format emerged as a way to take advantage of the best features offered by both JPEG and GIF. Using alpha channels, this format gives you a choice of various levels of transparency, including completely transparent backgrounds useful for logos with a quality higher than GIF can provide. PNG is also the best format for images requiring fade effects.
If file size isn’t an issue, PNG can be used to preserve the crisp detail of complex images because the files retain all information when compressed. However, if graphics need to be resized on the web, some quality may be lost in the process.
Choosing the Right Format
With pros and cons for every image format, it’s up to you to decide which is best for any given web project. If you’re building a site with a lot of icons, pictures and graphic text, you’re likely to need a combination of formats for every page. When it comes to photographs and other colorful images, you may have to test whether JPEG or PNG produces the quality you’re looking for at a reasonable file size.
Check your images on multiple screens, including mobile devices, to determine if they display the way you want them to. Use a high-quality image editor to make any adjustments before publishing the final product.
Although common image formats may be interchangeable in some situations, it’s best to use each for its intended purpose. Choose formats made for specific functions to streamline your website, ensure crisp images on social media and give visitors a pleasing visual experience.