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Text Sizes and Screen Resolution

Filed under: Accessibility, News

According to clickdensity, there appears to be a link between user screen resolutions and text size settings.

Users with low screen resolutions (such as 640 x 480) appear to be more likely to use large text compared with larger resolutions of 800 x 600 or above.

The new user-metric site, clickdensity, has been analysing the results of their first three months’ worth of statistics and seem to have picked up on some distinct trends. The core data spanned 20 million visitor sessions from nearly 1,500 websites but clickdensity chose the limit their published analysis to text size and resolution settings from browsers that identified themselves as Internet Explorer. Obviously, accurate browser sniffing is almost something of a black art. Headers can be spoofed relatively easily so that Firefox, for example, identifies itself as IE. So I would be wary of reading too much into absolute figures but, with regard to identifying trends, I think it’s worth taking the data at face value for a moment.

The analysis focused on the IE Text Size settings of Smallest, Smaller, Medium (the default setting), Larger, and Largest and compared these to the recorded Screen Resolution. Medium Text was the most popular across the board (no surprise there). But when the figures for 640 x 480 screen resolution were examined, the number of visitors that appeared to be using Large Text increased by a factor of 150 (from 0.11% overall to 15.03% for 640 users).

A similar trend was noted with the very large resolution settings (1600 x 1200 and above).

Summary of clickdensity’s findings

  1. The vast majority of visitors (99.7%) use default (Medium) text size settings.
  2. Approximately twice as many visitors (0.2%) increase their text size than decrease their text size (0.1%).
  3. Users with very low (640 x 480) or very high (larger than 1600 x 1200) screen resolutions are at least twice as likely to change their text size settings (compared to users with resolutions from 800 x 600 to 1280 x 1024).

I suspect that the High Resolution/Large Text users have relatively normal sight and are simply re-adjusting the text size to make page readable. However, I do wonder if the Very Low Resolution/Large Text group represent partially sighted users.

So should we be testing designs at 640 x 480 using Large Text?

Published: November 17th 2007


  1. Stevie D

    The problem with this metric is that it tells us absolutely nothing.

    What would be interesting would be to see the pixel size of text on different users’ computers. I suspect that a lot of people leave the text on ‘medium’ or increase it to ‘large’ because web authors set a font-size that is substantially smaller than default.

    For example – when I read use it, I reduce the text to ‘small’, because when the text is at a natural size, IE’s default is larger than I find comfortable. But on other sites, such as a list apart, the designer has specified body text at 0.8em (a decision I strongly disagreed with at the time of the redesign, and still do), which means I have to increase the text size from my preferred size to make the tiny text legible.

    This becomes a vicious circle. Designers like tiny text, we all know that. Which means that people have to bump up the text size on their computers. Designers find out that a lot of people are using medium/large text so reduce the text size even more so that at those settings it looks like how they want it. So users have to enlarge the text even further.

    So without knowing the pixel height of the letters on people’s screens, we don’t know to what extent they are (i) choosing a preferred setting, based on natural font size, (ii) compensating for designers who think everyone wants to read microscopic text, or (iii) blissfully unaware that they are even able to change the displayed font size…

  2. Black Widow

    I agree that it would be stupid to read too much into this data. There are far too many unknowns. But I do find the suggested link between low screen resolution and larger text sizes rather intriguing…