size
Valid for email, password, tel, url and text input types only. Specifies how much of the input is shown. Basically creates same result as setting CSS width property with a few specialities. The actual unit of the value depends on the input type. For password and text, it is a number of characters (or em units) with a default value of 20, and for others, it is pixels. CSS width takes precedence over size attribute.

As css takes precedence over any size attribute it has been suggested that we remove all size="xx" from the xml form definitions.

Personally I would keep it for all frontend inputs as there may not be any css in the site template for this but I would remove all the admin input sizes as they are redundant.

@chmst @bembelimen