Best way to sort a multi-column list: Top to bottom or left to right first?

Question

I'm creating a long list of countries that span across 3 columns and initially I ordered them left to right and then top to bottom but a colleague of mine said it would be more natural to sort it first top to bottom and then left to right.

The overall height of the columns is small enough to be completely in view within the viewport on desktop so there's not a problem with having to scroll vertically to read through the whole column before moving to the next.

Are there some best practices surrounding this?

Curious to hear your thoughts, thank you!

Answer 1

Conventionally, like in newspaper column layouts, it's top to bottom, then left to right as your colleague suggests.

For your dataset, a list of countries with just 3 columns, there's going to be a lot more different eye movements needed from your user if you organise them left to right first - looking across 3 items, then back to the start of the row underneath, looking across 3 items, then back etc.. (If they're alphabetically ordered they can cut a lot of that out of course)

Going all strategic, what are you using this big long list of countries for? If it's for users to pick one, probably better to let the user type a couple of letters first and then have autocomplete suggestions.