Our email campaign editor automatically decides whether the image should be made constrained by 50% for high-definition displays or not. This option makes sure your image looks great on high-definition displays that are commonly found on mobile devices (iPhone, iPad) and latest computers (4k displays, Apple Retina displays).
How it works
Once you upload an image to your email its resolution is checked. In case the image has a resolution of at least 2x the resolution of image position, it will be constrained and look good on high definition screens.
Let's say you have an image that is 1000px by 400px and the image position you are adding it to is 500px by 200 px. In that case your image will be shrunken and will not look blurry on phones, tablets or other high-definition screens.
If you have an image that is of lesser size than 1000px by 400px and try adding it to the same position (500px by 200px), it will not be constrained by 50% and might look blurry on high-definition screens.
Bottom line - you should make sure that your images are of high resolution to get the best results and sharp looking emails.
A visual representation of how it works is provided below.
Recommended image sizes
Different email content blocks have different image positioning and require different sized images. To be sure all images on your emails look sharp, always upload images with at least 2 times higher resolution than the position itself.
You can always know the width of the position by checking on the placeholder (see tow examples below). You should not worry about the images height, as it will automatically adapt.
You can also always know the size of the image you are about to use by checking the details of it on your Image Library (see image below).
Example 1. Suggested product image size in this arrangement is at least 238px by 238px.
Example 2. Suggested image width in this arrangement is 576px and the height would adapt to keep the appropriate proportions of the image.