The 80/20 rule for accessibility testing

Earlier this week, I was looking at data from a recent accessibility audit and had a lightbulb moment. I noticed that the majority of issues found during a site-wide audit were discovered in just the first few pages tested.

A few things contribute to this result:

• Those first pages were key landing pages, usually with the most traffic
• Many global styles and reusable components appeared on these pages
• Repeat issues may appear on subsequent pages, but they were first identified in this small set

You’re probably already familiar with the 80/20 rule, also known as the Pareto Principle. It’s shocking how often it applies to absolutely everything in life.

So I’m calling this discovery the 80/20 rule for accessibility testing, which states:

80% of accessibility issues across your website can be surfaced by testing only 20% of the total pages.

If you have a website with 100 pages, the testing might break down like this:

• Homepage and 3-4 key pages: 75-80% of issues surfaced
• 10-20 secondary pages: 15-20% of issues surfaced
• Everything else: 5% of issues surfaced

Here’s the key takeaway: Identifying 4-5 key pages in your planning phase can help you find the majority of accessibility issues across your entire site.

Don’t hear what I’m not saying. I’m not suggesting you skip testing every page. You should still plan to address accessibility issues site-wide. You can just expect the volume of errors on the remaining pages to be far lower than that initial batch.

If you’re a small business owner wanting to make your website more accessible, this is a huge win for you!

Performing accessibility testing on every page can seem daunting, but testing just a few key pages is a manageable task. Plus, it’s a massive return on investment if you’re surfacing 75-80% of the issues that appear across your entire website.