Great question — there's a common misconception here that's worth clarifying. Klaviyo's documented best practice is not 1200px, and it's not primarily about DPI or specific inboxes like Apple Mail.
Here's what the documentation actually recommends:
Email template width
- The 600px email width has become an industry standard in email marketing because historically, the average size of a viewport in all popular desktop email clients was between 500-600px
- By setting the width of your email to 600px, you can ensure that, for the average viewport size, your recipients won't have to do a lot of horizontal scrolling to see all of your content
- Klaviyo highly recommends designing your emails at a width of 600px so they look great on desktop clients, and Klaviyo will render emails responsively across smaller screens like mobile devices
- Emails designed to be much wider have a higher potential to look skewed when scaled down on a mobile device unless carefully designed and optimized
Image sizing within that 600px frame
For the images themselves (not the template), Klaviyo's guidance is:
- Across the web, using 72dpi resolution is best practice. Try to keep your images between 600 and 1000 px in width and less than 2000px in height for full-width images, in order to balance image quality and loading speeds
- Note that a full-width image at 72dpi will often be larger than 1MB, and reducing the size of the image may result in an image that is visibly blurry or low quality
So 1000px width is the top end of Klaviyo's recommended range for full-width images — not 1200px. Going wider (like 1200px) isn't a documented Klaviyo best practice, and it's typically driven by designers wanting extra resolution headroom for high-DPI (Retina) displays, not an official platform standard.
A few practical notes from the docs:
- The maximum image file size supported by Klaviyo is 10MB. However, we recommend using images that are 1MB or smaller, as larger images can load slowly, leading to a poor recipient experience
- For Outlook specifically, a common problem in Outlook inboxes is images that become stretched or oversized — to avoid this, set a width for every image block, using 600 px (or whatever width your email is set to) for full-width images
From our experience: Some designers do export at 1200px or even 1600px specifically to account for Retina/high-DPI displays and to avoid visible pixelation when Apple Mail or other clients render images at 2x scale. This isn't wrong — but it's a design choice for image sharpness, not a Klaviyo platform requirement. If you go this route, make sure you're still explicitly setting the display width to 600px (or your template width) in the image block settings, and watch your file size — a 1200px image at high quality can easily push past the 1MB recommendation and slow load times. If load speed and consistent rendering matter more than max sharpness on Retina screens, sticking to the 600-1000px documented range is the safer, more tested path.