Revisiting ALL UPPERCASE LETTERS vs. Upper And Lower Case

Picture of a sad robot faceI’m sometimes surprised by which of my blog posts people get passionate about. Take, for example, my post on whether all uppercase letters are inherently harder to read than upper and lower case. I wrote the post back in 2009, yet someone posted a comment on it today, 8 years later. And last week someone said the post was “utter BS”.

Since the all uppercase topic seems to still be hotly debated, I thought I’d write a quick update. It appears there was a research study done in 2007 that I missed when I first wrote the post. The research confirms, as I said 8 years ago, that:

  • All uppercase letters are not inherently harder to read.
  • All uppercase letters don’t slow down reading speed.
  • In fact, in this study, done with both normal vision and low vision readers, people with low vision performed BETTER with all uppercase letters, presumably because they were larger.
  • This better performance effect with all uppercase disappeared when they increased the size of the font so that it was large even in upper and lower case.
  • All uppercase letters did  not slow down the normal vision people.

It’s a small sample size, but it was statistically significant, and so far as I know there is still no research showing the opposite, so, I’m sticking to the idea for now, that all uppercase letters are not inherently harder to read.


Aries Arditi and Jianna Cho;. Letter case and text legibility in normal and low vision. Vision Res. 2007 Sep; 47(19): 2499–2505. Published online 2007 Aug 6. doi:  10.1016/j.visres.2007.06.010

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3 Replies to “Revisiting ALL UPPERCASE LETTERS vs. Upper And Lower Case”

  1. I think it’s important to acknowledge that even if there is no reduction in readability, there is definitely a perception that all caps is undesirable in certain circumstances to a significant number of people (like in comment sections :-). As a result, a reader may simply choose not to read something that is in all caps. Thus, it does become a usability issue if you want a user to read something and they happen to be one of those people who dislikes all caps and thinks it is harder to read.

  2. Also, USING ALL CAPS is pretty much the written equivalent of yelling to a lot of people. Probably because it’s commonly used to emphasize things.

    Which, of course, is more of a unofficial –but commonly agreed upon– etiquette rather than a actual fact. But some people are REALLY passionate about this. (It’s actually funny because, besides that, there really is no true relation between it and yelling.)

    I guess there could be some sort of nocebo effect in people with a bias against all caps, no?

  3. ALL CAPS can cause confusion in some industries where use of acronyms is prevalent, such as Software Development and Telecommunications, especially in the Video sector where channel names, package names, site names, and acronyms are used in development and change management:
    – Which words are names?
    – Which words are acronyms?
    They can be harder to distinguish.

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