FORMS: When to use dropdowns, and when to use dynamic lists?

Question

Interesting that I couldn't find a discussion of this already.

When should we use dropdown selects, and when should we use dynamic lists (updated as you type) in web forms?

My opinion:

Dropdowns are better when:

• you don't have too many items to choose from (30 or less?)
• your audience is not very familiar with the choices of your dropdown, and would thereby benefit from being able to look at all the possibilities

Dynamic lists are better when:

• you have a LOT of items and having to display them all//scroll through to find what you need would suck (ex: country selectors)
• you know your audience is well-familiar with all (or nearly all) possible choices and can reliably enter it themselves (ex: country or city selectors)

Other reasons // situations to choose one over the other?

Answer 1

The dropdowns always generate the scroll problem, as Harald already mentioned, but they are ok for a few items.

If you have a lot of options, though, and the items are somehow known by the user, you could use an autocomplete field. I've seen this use at airline ticket purchasing websites, where you have to select you airport of destination. As an example, take a look at what Kayak does.

Answer 2

Typical answer is "it depends on the circumstance", real answer is what my testing shows works best and can be the most accessible and usable for the task.

Accessibility matters a lot to me and many dynamic lists simply fail, and when they don't fail accessibility, often they get user complaints, mostly from newer web users who find anything that tries to fill in for you or jumps around distracting.

My mother, a competent user, called me to fix her computer last week because of the way it was jumping around when using Google...

Answer 3

I personally don't like dropdowns you you have to scroll through them, a lot of websites seem to like doing that with the country selection, so that means probably 15 items or less.

You can still let people look at all the items in what you call a "dynamic list" if implemented with a plain list with selection and a input box that filters the items in the list.