What are the pros and cons of using 2 fonts on a single page/throughout an application?

Question

As a very relatable example, we have Android OS (since which version I do not remember) using 2 fonts, one for headlines and one for the rest of the text.

As in the image, we can see that it uses 2 fonts. Noto for Headlines and Source Sans for body text. By default, I think the combination is Circular+Roboto.

So, Generally, the question is:

" What are the pros and cons of using 2 fonts on a single page/throughout the app".

Answer 1

Pro Con Artists?

This is not really a "pros & cons" type of decision, it's a design choice which is ultimately more subjective than objective.

The only "con" I can think of is that you need to use more than one font file (increasing resources), nevertheless this is trivial and adds only a tiny amount to the memory footprint of the app.

A better way to look at it:

1. It is a common design practice to use multiple font families in a design, and this certainly goes for user interfaces.
2. Multiple fonts (when used appropriately) can add readability and enhance user engagement by using different fonts, weights, and/or styles to different functional areas of the UI.
3. Using a particular font design/weight/style helps cognitive accessibility of the app though visual separation, emphasis, and definition of functions, controls, dialogs, etc.
4. Conversely, using a single font-face design, weight, and style will often feel "stagnate," banal, flat, and uninteresting.
5. Designs using multiple typefaces tend to have a greater feel of "depth", contrast, and dimensionality.
6. Nevertheless, too many font designs, and mutiple fonts used without a valid "reason" or design objective will tend to be chaotic, cluttered, and obtuse.

X = WHY

As I think about it, this is kind of an X/Y problem. You're asking to solve perceived problem X, but the actual problem is Y.

In this case, the original question is a fundamental "design 101" question — and by asking it, a seemingly unrelated answer is probably most helpful. So here's the "long term useful" answer:

Take a life drawing class.

Your local college or community college should have one. Find a class that teaches the Nicolaides method of drawing.

WHY? Because:

I recommend life drawing for ALL artists, even photographers and actors. Why would a photographer or an actor need to learn to draw??

Because it's not about drawing. A good life drawing class will give you the tools to draw ... but the real benefit is more subtle, and simultaneously much greater.

Life Drawing teaches you how to see. How to see the world as an artist, designer, illustrator. That is the real benefit of a proper life drawing class.

The structure of the class is that a live human model (nude) poses for class to study and draw. The human form is among the most difficult & challenging. At the start of the class, the model will go through dozens of poses, 15 seconds each. In this time you do "gesture" drawings with charcoal, without looking at the paper, just making a mass in the shape of each pose.

As class progresses, the poses get longer, and your instructor will give you different objectives to work on. The stated objective is developing hand eye coordination, but the underlying objective is learning to see.

Though this practice, things like composition will become second nature. A question about using multiple fonts in a design will seem trivial. And you'll instantly see everything that is wrong with that UI image you posted (Yikes! it's making my brain itch!!)

Please let me know if you have other questions.