Hello @Chloe_allplants,

Thanks for sharing your question with the Klaviyo Community!

Because dark mode is a preferential setting used on the device your recipients are opening their emails on, there wouldn’t be a way to detect when a recipient is using dark mode or not. One way you can attempt to measure how many of your contacts prefer dark mode versus light mode would be simply asking them! You can pose this question within either a signup form or within an email which can be used to tag your contacts with a custom profile property to calculate this data out yourself. I’ve included some Help Center articles below which can help you set these sort of signup forms or emails up as well as further understanding custom profile properties:

• Guide to Properties
• About Custom Properties
• Update Profile Property Action Use Cases
• How to Use Links to Collect Information About Your Recipients

In addition, I would suggest taking a look at @retention’s great comment in the Community post below which discusses dark mode and how it effects email templates:

I hope this helps!

David