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Does font size and color affect usability?

If I were asked what the single most argued point of Web design is at BrandLogic, it would unequivocally be font size and color. This is an argument that occurs both internally between graphics designers and Web strategists, and externally when we present our concepts to clients. Everyone seems to have a thought about what the ideal font size/color is, and it is always the one item about which they are not too shy to comment. Inevitably, reference is made to some unknown study that claims 12pt black type (or some other combination) is ideal. And what is the number one rational for their point of view? Legibility/usability.

Please allow me to clear up one misconception. Legibility and usability do share a relationship, specifically for a user to find a block of text usable it must be legible. However, this relationship does not mean that legibility is usability. Usability—with regard to the Web—emcompasses the Web site as a whole. There are many things to consider. Audience: who are your users? There is also content: Is it appropriate for the audience? is it clear, on brand, on point? There are user interface elements such as labeling, focal points, and action feedback. And of course there is graphic design, which at a minimal encompasses layout, color, graphics, line length, page size, and yes, typography.

Typography itself is an art form that is much more than font size and color. Thanks to CSS we Web designers are finally learning this. I remember an early lesson when I was a seasoned Web developer, but naive to design (and I probably still am). A very brilliant, and thankfully patient designer was rebuking my challenges that his chosen font size and font color made for illegible content. To my astonishment, he did not disagree with me, but simply pointed out that we had only applied two attribute of this typography specs. He gave us a quick lesson on typography, probably one-one thousandth of what he knew on the subject, and asked us to adjust some other attributes, specifically leading and kerning (letter-spacing and line-height). To my astonishment, those simple changes drastically affected not only the legibility, but also the feel of the page as a whole. The page felt lighter, my eyes could track the text much easier, it was a more enjoyable experience.

Still, even with more granular, and properly applied control over fonts, concerns about size and color still come up. Why is font size such a contentious issue? First off, it's an easy target because size and color preference are just that—preferences, and that makes them by nature very subjective. I contend that the major problem is there are no hard and fast rules for what color or size a font should be. It is very audience and design dependant. To some degree, the design will drive the decision of font size and color, but in my humble opinion, a good designer will let the needs of the intended audience drive the design.

Industry experts have weighed in and given us their opinions. Leading Web usability expert Jacob Nielsen once wrote: "Tiny text tyrannizes users by dramatically reducing task throughput." [1] A bold statement, and not without truth! And in the same article, he goes on to make his recommendations—both to browser makers and Web designers. But the rules are not concrete, or at least I do not view them that way.

It boils down to this: font size and color alone can affect usability, but you must examine the Web site as a whole. Conduct a usability test on the site, and consider these guidelines with regard to font size and color:

• Ask the users to read a page.
• Refrain from asking them subjective questions like, what do you think of the font size?
• Instead, ask them questions about the content and while you are noting their comprehension, see if they offer opinions about the legibility.
• At the end of the test, ask what they think of the design of the page as a whole.
• At the end of the test, if they haven't already offered the information, ask what they thought about the legibility.

Don't let a good design be altered by a subjective opinion, but also, don't ignore the empirical evidence if it shows your users are having trouble reading your site. If your time or budget doesn't allow for a usability test, then point to other sites you have done that use a similar size font and were also tested. Also, look for popular, well-respected Web sites in the same industry that cater to the same audience. Perhaps they use a similar size and/or color font. This of course goes against my statement that design must be treated as a whole, and these arguments are not concrete, but maybe can provide some supporting evidence that your font choices are OK. Your client wants reassurance that they are not making a mistake.

Too often I have seen the comments of a few "squeaky wheels" push a client into decision that has a much larger, negative impact. Remember, you need to help educate your client about design and usability, just like someone most likely helped to educate you.