Why automated accessibility testing tools are not enough

To accurately check a website for WCAG compliance, you need more than automated tests, you need human evaluation.

Accessibility, for a long time, was often an afterthought in the development process of many websites and mobile apps. But, whether it’s driven by compliance regulations, Google algorithms or simply, that it’s the right thing to do; we have seen a shift in the industry towards creating digital experiences that are inclusive of more people.

However, we still have a long way to go and accessibility testing is a vital part of the journey towards creating a digital world where everyone can engage and participate equally.

Accessibility testing is the process of checking if websites or mobile apps are usable by people with disabilities (permanent, temporary or situational) by assessing them against international accessibility standards – Web Content Accessibility Guidelines (WCAG) 2.1.

This can be done in two ways: by using automated tools or carrying out a manual audit.

Automated Accessibility Testing

Where manual testing is typically carried out by a specialist test analyst, anyone that has access to a tool can run an automated scan. The tools available fall into three main categories: browser extensions, web-based and desktop-based.

Browser Extensions

One of the easiest tools to use, extension tools allow you to check any page open in your browser; performing singular checks, they give you instant results.

Web-based tools

When it comes to multi-page scans, web-based tools are the most popular. Where browser extensions perform singular checks, web-based tools can simultaneously audit multiple pages.

Desktop-based tools

Desktop tools perform the same scans and offer the same coverage as a web-based tool, with the only difference being, the scan is performed by an application on your local machine.

The Benefits of Automation

Cost: many of the browser extensions are free to use, which means that if small budgets are a factor the barrier to entry is removed.

Speed: web-based tools can simultaneously audit hundreds of thousands of pages across multiple sites and provide results more quickly than a manual audit. And, the output of an automated scan can increase efficiencies in the manual test effort by identifying areas where there is a high likelihood of further issues being present.

Repeatability: automated tools can be integrated into the development lifecycle and tests can be run when features are added or updated or scheduled at regular points between full manual audits.

The Limitations of Automation

Limited coverage: automated tools cannot test websites against all the WCAG success criteria and will only reliably find 20-30% of accessibility issues. Many of the WCAG guidelines are written as testable criteria for objectively determining if a webpage satisfies them, therefore can’t be passed by an automated test as they need human evaluation.

False positives: not all tools are created equally and the levels of coverage vary between them and are known to generate false positives; where a success criteria can be tested and passed by an automated tool, the result could be incorrect.

Technical knowledge: even though almost anyone could run an automated scan, the results and language that is used often requires an existing level of web accessibility knowledge and someone with none or limited experience might struggle to interpret the results correctly.

Manual and Automation: A Combined Approach

Automated accessibility scanning tools can be a great addition to the digital tool belt, but you cannot rely on them alone when assessing the accessibility of a website. When an automated test is passed, this means that no errors were identified by the script the tool ran, not that the website or content is accessible.

Automated tools are great at giving an overview into the general accessibility of a website, but they are most effective when used as a complementary tool alongside manual audits forming part of a wider accessibility strategy.

Accessibility is an on-going process and by taking a combined approach, you can identify issues earlier, reduce development bottlenecks – saving money while increasing the reach of your website.

At Zoonou, we use automated tools to supplement our manual WCAG compliance audits in a number of ways; to help identify key areas when creating test scripts; to increase coverage during test execution; and for ongoing maintenance checks between each audit. For more information on our accessibility testing services, head over to our service page.


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