image sizes for website

This is a quick question that anyone in the know can answer for me. Im building a site and want to get the details right.

I will be using landscape and portrait images. I read that a maximum size of any image should be 2500px.  Does this mean the longest length of the image, or relevant only to the width of any image? (which is what the help page seems to indicate, but seems logically just wrong)

thanks in advance

Related to total size of the file. 

I'm confused by the use of the term 'wide' and then later 'along its longest edge'. This presumes landscape images doesn't it? If my portrait image is sized to 2500px on its width, the longest edge is much bigger.
Am I missing the point somewhere?

How is a site wide banner or page background image going to be viewed? Portrait or landscape, that determines the longest edge. 

Hi @Licol

These are simply recommendations from Squarespace.  In reality you can use any sized image you like.  If you use an inline image served by Squarespace; they will resize it.  But if you're using background images/developer mode; you can bypass this.

It's simply a recommendation to ensure that you are using optimised images.

Hope this helps!

Andrew
DCODE GROUP