With more and more of us choosing to open emails via our mobile devices as the preferred option, it’s really important to be aware of you to ensure that our viewers have the best possible viewing experience. 

If your recipients are using a cellular network to download and read emails, then it’s important to ensure that everything contained within our email marketing is optimised for speedy downloading on a slower network.

Unsubscribe rates dramatically increase for emails that don’t display all of the content quickly and accurately. The main culprit for download and rendering speeds are images, if your campaign uses images, then they need to be optimised properly for usage on cellular networks.

Image file sizes

This is the first area to look at when thinking about the mobile viewing experience. Using images is a great way to maximise conversions as they really help to build your brand identity and display your products in the best possible light. 

It’s very important to keep an eye on the file size (kb) of your images. It’s quite common to see images if they haven’t been optimised at over 200kb. Whilst these may look lovely and sharp, they will be too slow for your mobile device recipients to download.

As a rule of thumb, you should always aim to keep your image sizes below 100kb as an absolute maximum. It’s important to maintain a good balance between the visual quality of your image and the file size. Any decent image editing software will let you try different settings to see what works best.

There are also image-optimising websites that will handle all of the heavy lifting for you. You can upload your source file and it’ll then automatically reduce your file size, whilst retaining the original visual quality of the image.

Image pixel sizes

The next area to look at is the width and height of your image in pixels. The standard width for an email spanning 100% of the viewing pane is 600 pixels wide, there is nothing to be gained by having images larger than this size.

If your source image pixel size is larger than 600 pixels, then this can make life difficult for you in terms of file size. If the image width is too wide, then it can be a struggle to get your file size below 100kb, whilst still retaining the viewing quality.

You may find that your image starts to look blurry or pixelated if your file size is below 100kb.

Some email readers can also struggle to render images with a large pixel width. Outlook, for example, has a peculiar quirk; where it will flip a very wide image on it’s side, which results in your email marketing becoming a jumbled mess.

In summary…

The rule of thumb for your email marketing images is to keep them within 100kb file size and width no wider than 600 pixels. Following these guidelines should offer a consistent viewing experience for recipients using cellular internet connections.