I'm currently working on revising some web design standards at work, and
am trying to sort out a minor debate over sizing input field lengths
In my experience, the guideline for determining the size of input fields
is to use a size similar to the information that the user will be
entering. So, a field for a 16-digit credit card number should be about
16 characters long; a field for a 3-digit CVV code should be about 3
digits long. For data that is not so determined (email address, proper
names), an average or estimate length should be used. The intention is to
provide subtle hint to the user that helps them understand what they are
supposed to enter.
However, the standards I'm reviewing suggest that all input fields should
have the same width, so as to provide visual consistency within the page.
The size is determined by an average length across all fields. The
argument for this is to make the page easier on the eyes, so that the
field labels and input fields aren't creating a jagged effect. It seems
to me that this approach is more geared towards the visual or graphic
design side of thigns though, rather than focusing on usability.
I've tried to do some research on this topic and have found a few sources
with limited information. Most of the sources imply that the first
approach (sizing based on specific content) is the better approach, but
don't give an explanation as to why. I'd really appreciate it if anyone
could direct me to any sources that might provide some hard data on this
subject, whether in software or web design.