I'm not sure what to call them, but anyone know of research on the effectiveness of including the ability to resize text onscreen via a buttons/toggle. I mean the "aA" button you still sometimes see or the "Font size: - or +"

Is there evidence that these are used? Know of any usability research that directly focuses on their use by the elderly and other who might have accessibility concerns? Are they worth doing?

In general, I feel like I see the tool less than I used to. Modern browsers to a better job zooming and of course designing for mobile and other devices adds another level of complexity. In my case, I'm thinking about this for a web-based app that involves a fair amount of reading and is aimed at a older audience.

A couple of examples:

LA Times


3 Answers 3


From my practice and researches I have seen that giving an onsite resizing option is more handy than leaving it on the browser.

For elderly people it is always best to have options upfront and well placed so that they can use it. In Browser mode, they need to use multiple key combinations to zoom in and out which they are less likely to use. Moreover, the zoom option inside the browser menu might be hard to find. Placing a Zoom in and out option on the page helps them to understand what they can do with that.

It is also seen that the elderly people generally scans the whole page before they proceed to do some action. In that case, having such option on the page will get their attention when they scan the page.

In a lot of countries government has also made it mandatory to make the public sites to be accessible and re-sizable text is one of the prime contenders in Accessibility Norms.

  • 1
    Here's a (pretty small) usability test that seems to agree with you, saying some elderly users (3/8) read through the whole page before interacting with it, and that while they all seemed to want to resize the text, very few knew how to do so in the browser being tested (although I tend to suspect that some browsers exhibit this issue more than others; Safari—with some tweaking—can make this very easy indeed).
    – Kit Grose
    Jul 11, 2012 at 5:44
  • Good feedback -- placement of these is a concern, I think. I've often seen these text size tools lumped in the with print/email functions as tiny little icons. Not easy to see for someone who already is having problems reading tiny text. Definitely don't think we can rely on anyone using the "zoom" tools within browser. I barely remember how to use those.
    – Voodoo
    Jul 11, 2012 at 19:18
  • Yes.. Designers generally take the privilege of placing it somewhere where it is easy to accommodate them. For my designs, I try to give them importance by making it somewhere in the header but with a nice and segregated background so that people don't miss them. Also it is a must that once a page has been re sized it is same when the user navigates to the next page.
    – ajayashish
    Jul 12, 2012 at 5:25

At the recent Usability Week put on by NN/g in Seattle in November 2012, this subject came up. They said that their research showed that hardly any users increase or decrease font size by any method other than native browser zoom functions.

They said in their studies it was very clear that users who have trouble reading small text are very used to using their browser's native function, so that is their default action.

Additionally, they said that there is no standard convention for placement and design of font size increase/decrease within the page itself. For placement, I agree. Sometimes it is within the page (maybe near a byline for a news article). Sometimes it is in the utility bar at the top. Users are not conditioned to know exactly where to find the feature and they don't know exactly what it will look like.

In contrast, they know how their browser's native functions work. It works the same, it looks the same, and it is located in the same place for all sites because it is a function of the browser not the site.

Of course all of these studies are behind a paywall so if you really want to know their details I'm sure they'd be happy to sell you a copy of their research.

However even on your own, try adding some Google Analytics event tracking to the controls in your page if you already have them and see if they get used.

My recommendation, however, would be to spend time making sure that your site scales well under magnification instead.

Update: this is a free report from NN/g on usability guidelines for the web. I haven't read every page yet but it doesn't seem to address the specific topic of using in-browser text resize feature.

However it does provide a great insight into HOW people using technology like screen readers or magnifiers use a page and what impact that has on the design.

There are several examples that support my original recommendation, which is to spend more time making sure your site scales well under mangification/zoom. For example:

Participants in our study told us they cannot magnify some sites with their screen magnification software. When this happens, they usually just leave the site. Some users said they’d call a sighted friend to help them use the site. Regardless, they could not use the site on their own at all, and were frustrated by this. In the tests in Japan, one participant showed us a website that he could not magnify. The site designer specified the fonts in pixels, in the style sheet, making magnification and normal font enlargement impossible.

On the subject of whether a user with vision problems will "know" how to use tools other than in-page controls that you add:

If you have never seen a screen magnifier, try to find and use one. As you’ll see, the results are very different than simply increasing monitor resolution or selecting the largest text in your browser. Users working with screen magnifiers make text big—really big. To see an entire page, they might need to scroll horizontally and vertically many times. The bigger the page, the longer it will take them to see the whole thing, and the more difficult it will be for them to remember everything on it.

Our participants were very adept at using their screen magnifiers. They knew how to zoom, change contrast, filter colors, and most importantly, scroll vertically and horizontally.

Some users chose to simply highlight text, or chose select all, because highlighted text appeared as white text on a dark blue background.

The key take away here is that if someone truly has vision problems, they are going to know how to use tools that are much more helpful to them than any widget you add to the page. How your page looks when using these tools however does take some planning on your end.

Here is a video that illustrates what one of these screen magnifiers looks like and how they are used.

  • Any chance you have a citation for this? This is great info and something that I always thought was the case. Nice to see there is research out there on it.
    – DA01
    Feb 4, 2013 at 18:28
  • Unfortunately the substance of my answer is based on a dialogue that occurred during one of the sessions, and I suspect that the supporting study is available through NN/g for a fee. In writing the answer I did attempt to locate freely available information to support the argument, however I was unable to find any. In the session they did have a few video clips from usability studies showing users ignoring the feature, but that too is not public. Feb 4, 2013 at 18:50
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    I expanded upon the answer a bit to provide some context that supports my recommendation even though I couldn't find the exact study that addresses the particular technique in the OP's question Feb 4, 2013 at 19:10
  • Very good answer @charles - thanks for the expanded details. I'll leave the original answer as accepted, but following your approach makes a lot of sense.
    – Voodoo
    Jul 29, 2013 at 21:13

I don't have any evidence to demonstrate the usefulness or otherwise of these links, but I do have an explanation for their continued use:

Many large websites (especially those run by governments) are expected (or, at least in Australia, legally required) to conform to the Web Content Accessibility Guidelines (WCAG) 2.0 requirements.

One of its requirements, 1.4.4 Resize text states:

Except for captions and images of text, text can be resized without assistive technology up to 200 percent without loss of content or functionality. (Level AA)

And in its guidance on how to meet that requirement, they suggest that the links you describe above as one of their "sufficient techniques" (technique G178).

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