Interactive Marketing Design Tips: JPGs, GIFs and PNGs – Optimizing Imagery for Email and Web - Email Design

What image formats are most appropriate to use when I’m building an email? Let's explore the three common image file formats appropriate for email: JPGs, GIFs, and PNGs.

JPGs 
The file name .jpg stands for Joint Photographic Experts Group. It’s one of the most common image formats, allowing for compression adjusting to benefit speedy load times for web display. The format utilizes compression that is best for image slices that include photography and images that need a higher amount of data to show detail. When you save the image for web use (often referred to as "save for web" in Photoshop), you can choose the appropriate amount of compression, allowing file size reduction as needed while adjusting the image quality and compression.  

ExactTarget tip: An image should be at or under 200KB in order to be uploaded into Portfolio in your account. 

For images that utilize line drawings, vectors, and other textual or iconic graphics like logos, it's best to use a GIF file format instead.

GIFs 
The file name .gif stands for Graphic Interchange Format. It also uses data compression to reduce file size while maintaining visual quality, accurately conveying crisp line art. Because GIFs are great for sharp-edged line art with a more limited palette of colors, they also work well for small animations (known as animated GIFs) and low-res film clips. GIFs are not best for photography because they use a limited palette of 256 colors. 
 
Another option, comparable to the .gif, is known as a PNG.  

PNGs
 The file name .png stands for Portable Network Graphics. PNGs, specifically PNG-24, include transparency and will mostly work in email. PNGs are best for conveying intricate transparency like a rounded corner or a partial gradient, and are actually bitmapped images that were created to improve upon the GIF. We mostly commonly see rendering challenges with PNGs occurring in Outlook 2003 and earlier. These email clients use the version of IE currently installed on the machine to render emails. If that version is IE6, PNG files are not supported by default.

PNG support in email:

We commonly see 7-15% of audiences using Outlook 2003
Worldwide use of IE6 is estimated to be 6%
US usage of IE6 is estimated to be <1% (via http://www.ie6countdown.com/)

As a rough estimate, this would affect less than 1% of the total audience and isn’t a major concern, but it's good to be aware in case a subscriber or employee raises an issue.  

For additional interactive marketing tips and advice, check out our Email Design Toolkit. You can also read some of our past blog posts or follow @ETDesign on Twitter.