In email marketing, images play a pivotal role in capturing attention and conveying messages effectively. However, the choice of file formats, animation types, and image dimensions can significantly impact the success of your campaign. Here, we outline key considerations for using images in emails to ensure they are displayed correctly and efficiently across various email clients.
File Formats for Images in Emails
When selecting image file formats for emails, compatibility and performance are paramount. Below is a table of commonly used image file formats and their characteristics:
| File Format | Description | Support |
| JPG | Widely used for photos; good balance of quality and file size | Broadly supported across all email clients, no transparency |
| GIF | Supports animation; ideal for simple graphics and logos | Well-supported, but limited to 256 colors, transparency can be used |
| PNG | Supports transparency; good for logos and icons | Broadly supported, higher file sizes than JPG, transparency can be used |
| SVG | Vector format; scalable without loss of quality | Limited support; not recommended for emails |
| WEBP | Modern format; superior compression and quality | Limited support; not recommended for emails |
Animated Images
Animated images can add dynamism to your emails, but it's important to use the right format and understand their limitations:
- GIF: The most widely supported format for animations in emails. However, some email clients, notably former versions of Outlook (2007 to 2016 on Windows-operated devices), only display the first frame of the GIF. To ensure important information isn't missed, make sure the first frame is informative.
- PNG: Although the PNG file format can support animations (APNG), it’s not widely supported in email clients. As with animated GIF, sometimes only the first frame of the animation is shown.
Tip: Use Cinemagraphs instead of fully animated scenes. They typically feature subtle, looping animations that help keep file sizes manageable, as only a specific part of the image is moving, but the rest stays static.
Image File Size
Keeping image file sizes under 200 kB is recommended to avoid broken images caused by network interruptions or email client image caching issues. In addition, larger files can increase load times and negatively impact user experience.
Image Dimensions
For optimal display across different devices and email clients, adhere to the following guidelines:
- Avoid blurry Display: Image files should be of at least twice the size of their embedded size in the e-mail, e.g. If you are using a logo image that is embedded with a size of 200 x 100 px, then the image file should be at least 400 x 200 px to avoid blurry display on high-resolution screens. Note that there is no necessity using files with image dimensions three times the size or more of their embedded size.
- Maximum Width: Image files should not exceed a width of 1200px. There is no need to use larger images, as the display quality mostly stays the same, even if the e-mail is displayed on a high-resolution screen. Additionally, the larger the dimensions of the image file, the longer it takes to render the image if scaled down on smaller devices.
Best Practices
- Compression: Compress images to reduce file size without compromising quality. As a basic rule, the availability of pixel information is more important than the image quality itself. For example, it’s better using an image that has a width of 1000 x 400 with high compression instead of using an image with a width of 600 x 240 px with low compression.
- Alternative Mobile Images: Use these sparingly. Having both desktop and mobile versions of images can double the data downloaded, increasing load times, and rendering delays.
- File Naming: Ensure that image files formats are named correctly and not just renamed from unsupported formats, as the original format may still cause issues.
- Testing: Test emails across multiple devices and email clients to ensure images display as intended.
By following these best practices, marketers can enhance the visual appeal of their emails while ensuring compatibility and performance across various email clients. Properly optimized images can lead to higher engagement rates and a better overall user experience.