How many people have JavaScript disabled or unavailable?

In 2013, the UK’s Government Digital Service did an experiment to determine how many of their users weren’t receiving JavaScript. You might assume, as I did years ago, that the only two options were either that users would have JavaScript enabled, or have disabled it explicitly via their browser’s settings or an addon. Unfortunately, those aren’t the only two options. The majority of users that don’t receive JavaScript likely don’t do so by choice.

They found that 1.1% of users didn’t execute their JavaScript test. Of those, only 0.2% either explicitly disabled JavaScript or used a browser that didn’t support it. The remaining 0.9% did not indicate they didn’t support JavaScript, but were not executing the test.

‘noscript’ tags will only be followed by browsers that explicitly have JavaScript disabled or don’t support JavaScript at all. So a significant number of people had a JavaScript enabled browser but still didn’t run the scripts successfully.

It’s hard to know exactly why these browsers didn’t run the JavaScript, but a number of possible reasons are:

  • corporate or local blocking or stripping of JavaScript elements
  • existing JavaScript errors in the browser (ie from browser add-ons, toolbars etc)
  • page being left between requesting the base image and the script/noscript image
  • browsers that pre-load pages they incorrectly predict you will visit
  • network errors, especially on mobile devices
  • any undoubtedly many more I haven’t even thought about…

The takeaway? Do not assume that everyone has JavaScript, or will have it execute reliably even if they haven’t disabled it.

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