Browsers and operating systems usually have settings to make pages larger or smaller. This makes computers accessible for some users with low-vision and I've also seen it used temporarily for presenting, screencasting, or even personal preference.

I've seen two methods for enlarging content:

  1. Expose a scale factor (like 1.5 or 150%) to uniformly scale all dimensions
  2. Apply a scale only to font size so that text is the only element that scales

If a user has access to both #1 and #2, do they prefer one or the other? What scenario would cause them to select #2?

Gion Kunz asserts that there's no reason to even provide #2 as an option. Someone in the comments mentioned the eBook scenario, which relies heavily on font size scaling. But most apps are not eBooks. So why should we continue to support font size scaling? What scenario would it be used in?

  • 1
    I would also add, that even for ebooks, text scaling is a mute point unless reflow is available to prevent horizontal scrolling.
    – Neil
    Commented Apr 2, 2017 at 12:30

2 Answers 2


I guess, in 80% of the cases scaling only fonts is useless, cause the rest of the elements remain unscaled. This also may break some layouts as graphical elements remain at their original size. So scaling fonts may be useful only in two cases:

  1. When graphics is irrelevant or minimal, e.g. eBook
  2. When graphics dominates the text, so at some scale text is difficult to read.

The second case is interesting. Imagine you have a site which displays blueprints or maps of some sort. Instead of zooming in, the user zooms out to get an overview of the whole thing. If user applies scale factor to zoom out, the text may become unreadable. Now, you need to stay at the scale, but increase font size. Suddenly, the option of scaling only font becomes very useful.


Especially on mobile, there is a huge difference between scale factor (zoom) and font size.

If I zoom a webpage to 200%, then I only get to see half of the page and have to pan left and right to read text.

If I adjust the font size to 200%, then all text is wrapped and I don't have to pan. (Except when there are long words that don't fit the screen anymore.)

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