SEO Spider

How To Perform A Web Accessibility Audit

Introduction

Accessibility audits are an important way of identifying barriers to users with disabilities, and delivering an inclusive and rich experience for all.

Providing a compromised experience to any users will inevitably have an impact on both user satisfaction, and site performance. There are also important legal and moral obligations for websites to ensure that they are equally accessible to everyone.

This tutorial shows how to run an accessibility audit of a website at scale using the Screaming Frog SEO Spider, which integrates the open-source AXE accessibility engine for automated accessibility validation based on the Web Content Accessibility Guidelines (WCAG) set by the W3C.

This is what powers the accessibility best practices seen in Lighthouse and PageSpeed Insights. The full AXE rule set contains over 90 different rules to identify accessibility issues for website users.

It should allow users to improve their websites to make them more inclusive, user friendly and accessible for people with disabilities and those without, such as mobile users, older people or those with situational limitations.

Please note – An SEO Spider licence is required to perform the accessibility audit below.

1) Enable ‘Accessibility’

Click ‘Config > Spider > Extraction’ in the top menu and enable ‘Accessibility’.

This means accessibility checks will be performed against all HTML pages on any website crawled. However, it does also require JavaScript to be enabled.

2) Set ‘JavaScript’ Rendering

Now click ‘Config > Spider > Rendering’ and in the dropdown choose ‘JavaScript’.

This means the SEO Spider can render web pages while crawling using Chromium to run the AXE accessibility audits.

3) Connect to PSI

As an optionable step, you can collect a Lighthouse accessibility score from 0-100 for each page, as an indicator of accessibility performance.

This can be pulled in by connecting to Lighthouse via the PageSpeed Insights integration (‘Config > API Access > PageSpeed Insights’), and selecting ‘Accessibility Score’ under the Metrics tab.

Each score will then be viewable in the Accessibility tab, covered later in this tutorial.

4) Crawl the Site

Input the website to perform an accessibility audit into the URL bar at the top, and click ‘Start’.

The SEO Spider will then start crawling the website and analysing accessibility.

5) View the Accessibility tab

The Accessibility tab details the number of accessibility violations at different levels of compliance based on the Web Content Accessibility Guidelines (WCAG) set by the W3C.

Lighthouse accessibility scores are displayed against URLs (if enabled), and are a weighted average of all accessibility audits available.

Weighting is based on AXE user impact assessments and they are grouped by Good, Needs Improvement and Poor in the Overview filters.

The Accessibility tab includes filters by WCAG version.

The WCAG version filters contain over 90 rules within them to meet that level of compliance at a minimum. For example, WCAG 2.0 AAA contains 3 rules.

Accessibility Tab WCAG filters and rules

A summary can be seen in the Overview tab, which updates in real-time as you crawl.

Accessibility Tab filters in Overview tab

Rules are grouped by WCAG standards, which build upon each other and start from WCAG 2.0 A to 2.0 AA, then 2.0 AAA before moving onto 2.1 AA and 2.2 AA.

The Accessibility tab has the following rule groups with 92 rules across all filters:

27 Best Practice rules that do not necessarily conform to WCAG success criterion, but are industry accepted practices that improve the user experience.
56 WCAG 2.0 A rules that check for conformance to WCAG success criteria.
3 additional WCAG 2.0 AA rules.
3 additional WCAG 2.0 AAA rules.
2 additional WCAG 2.1 AA rules.
1 additional WCAG 2.2 AA rule.

To meet one of the WCAG standards in the tool, then all other violations in previous WCAG versions must also be passed – as rules are not repeated.

For example, to conform to WCAG 2.1 AA, rules in WCAG 2.0 versions should be passed as well.

The right-hand Issues tab groups by accessibility violation and orders based upon priority, which is mapped against the WCAG ‘impact’ level from Deque’s AXE rules.

Accessibility issues in the right hand Issues tab

All rules include an issue description and further reading link with more detail. Browse our accessibility issues library for more detail on each.

Which WCAG Version Should Be Followed?

We recommend reading about the WCAG versions. 2.2 is the latest version which was released in October 2023.

WCAG 2.0, 2.1, and 2.2 are designed to be backwards compatible, which means content that conforms to WCAG 2.2 also conforms to WCAG 2.1 and WCAG 2.0. There are 3 different levels of standard for each version, with A the lowest, AA the mid-range and AAA as the strictest.

We recommend consulting legal teams when evaluating level of compliance for each organisation and website. There are various laws, that might need to be considered such as –

Section 508 standards in the US require that all electronic content conform to the Web Content Accessibility Guidelines (WCAG) 2.0 level A and AA for federal agencies, and private entities with public funding.
The Americans with Disabilities Act (ADA) which mandates WCAG 2.1 A/AA as the criteria for measuring digital accessibility for state and local governments, their third-party contractors and software providers.
The European Accessibility Act (EAA), with most member states implementing WCAG 2.1 AA.

If you’re just getting started with accessibility, then we recommend the Accessibility Fundamentals Overview from the W3C.

6) Analyse using Lower Accessibility Details Tab

Granular details of accessibility violations can be viewed by clicking on a URL or multiple URLs in the top window pane, and then the lower Accessibility Details tab.

This highlights accessibility violations, guidelines, impact and specific location on a page of any issue.

You can right-click on any of the violations on the right-hand side, to ‘Show Issue in Browser’ and it will be highlighted in Chromium.

Alternatively, ‘Show Issue In Rendered HTML’.

Show Accessibility Issue In Rendered HTML

All data can be exported for URL(s) highlighted by using the ‘Export’ button. There’s a handy link for further reading against each rule.

7) Bulk Export Accessibility Violations

Accessibility issues can be exported in bulk via the ‘Bulk Export > Accessibility’ menu.

All violations can be exported, or the various WCAG levels.

Exports include detailed accessibility issues seen in the Accessibility Details tab, such as issue, guidelines, impact and location on page for all URLs.

8) Export Aggregated Accessibility Violations

You can also export an aggregated view of accessibility issues via ‘Reports > Accessibility > Accessibility Violations Summary’.

This shows the number of URLs with a specific violation, the guidelines, user impact, priority and % alongside a sample URL as a summary.

Aggregated accessibility violations exported

This can help better prioritise accessibility violations.

9) Consider ‘Incomplete’ Checks

The AXE accessibility engine has a ‘zero false positives’ policy, so there are times where it’s not able to tell if there is a violation or not with 100% certainty. It names these as ‘Incomplete‘.

The lower Accessibility Details tab displays these checks against URLs in the appropriately named ‘Incomplete’ section.

For example, for ‘Links With Same Accessible Name’, it requires context to know whether there is an accessibility issue and more investigation is required. It’s best to manually review these.

Many tools will hide these incomplete checks, but you’re able to export these in bulk via ‘Bulk Export > Accessibility > All Incomplete’, as well as at WCAG level.

Summary

This tutorial should help users perform an automated web accessibility audit at scale across any website using the SEO Spider.

However, this automated approach should not be the only way accessibility is evaluated, templates and pages should also be manually reviewed, with various tools available to test specific page level issues in granular detail.

Check out the following guides on accessibility and the different items covered in our tutorial –

Alternatively please contact us via support and we can help.