How accurate are the results?

Accessibility scores are based on the following test criteria:

  • Only the first 125 web pages of each website are tested
  • Only the main website of each organization is tested

The accessibility score looks at how accessible a website is, as measured against the latest international standard for web accessibility, WCAG 2.1.

In the UK and the EU, this is the latest standard required of all public sector websites by September 2020.

We believe Silktide performs the world’s most advanced automated assessment of web accessibility, so you may see issues you’ve not been aware of before.

Silktide loads pages in real browsers with JavaScript enabled. Silktide sees cookie banners, pop-up windows, animations, and other rich content as a human would. This includes the mobile versions of each website.

Silktide tests for mobile accessibility, non-text contrast, tabbed browsing and many other parts of WCAG 2.1. We don’t believe these tests are covered by other platforms.

Our tests cover all unambiguous criteria in WCAG 2.1. This means we only score websites for criteria that a computer can reliably assess by itself.

An accessibility rating does not purport to guarantee a level of compliance or non-compliance with the Americans with Disabilities Act.

The accessibility rating of every website in the Index is our opinion, as a result of a determination by Silktide’s proprietary software.

Unambiguous criteria in WCAG 2.1 testing

Silktide’s performs accessibility tests against unambiguous criteria. What does this mean?

It means that in some cases, aspects of WCAG 2.1 are subjective. Computers are not yet intelligent enough to understand the nuance of language as a human being would.

An example of a pass/fail test in WCAG 2.1 which could appear subjective is Success Criterion 2.4.2: Page Titled

The object of this criterion is to give each web page a descriptive title, to help users find content, orient themselves within it, and navigate through it.

The procedure for testing 2.4.2 is

  1. Check that the web page has a title
  2. Check that the title is relevant to the content of the web page
  3. Check that the web page can be identified using the title

A computer cannot tell if a title is relevant to the content of the web page because it cannot understand the context.

The Silktide algorithm tries to identify a wide range of cases where the title is likely to be not relevant. For example, if the title contains a string of nonsensical characters or has a file extension.

Some human intervention is always required when a Success Criterion requires some context.

Silktide provides a human the opportunity to manually check tests 2 and 3.

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