Types of accessibility audit

There are a number of ways to carry out the key elements of a web accessibility audit (measuring a website's level of accessibility in a systematic way against accessibility standards to create a list of actions to improve accessibility).

An accessibility audit can, for example, be carried out in-house or can use external consultants. It can be entirely manual or, more likely, use automated tools to assist the manual audit. (An automated accessibility check is not a full audit. Passing such a check does not mean that a site is accessible.)

An audit can involve every page on your website or a sample of pages.

Choosing type of audit

The choice of audit type that is right for your site depends on many factors. There is no single "correct" web accessibility audit that meets all requirements. Factors that affect what sort of audit is right for your website include:

• How much expertise is available in-house;
• The size of the website; and
• The nature of the publishing system.

We are going to discuss two types of accessibility audit:

• External expert audit; and
• Self-audit.

External expert audit

The preferred approach to web accessibility auditing is to buy in outside expertise. This approach has some strong advantages, such as:

• Access to specialist expertise in web accessibility;
• An independent, external point of view;
• Status of report enhanced by external, expert viewpoint.

In many cases, selecting external expertise for a web accessibility audit will be part of a tendering process. Running a tender for web accessibility auditing is described in more detail in section 9.  However, among the attributes that would recommend an external resource are:

• A track record of conducting accurate web accessibility audits;
• References available from existing clients;
• Web accessibility as a core offering;
• Suitable methodology and tools for conducting audits.

Self-audit

Self-auditing means that the site is tested by your own in-house staff. The advantages of this approach include the low cost and the fact that the staff are already familiar with the website. Self-audit can be included in quality management processes and carried out regularly.

However, it has disadvantages, including:

• It is difficult to find staff with the required skills;
• If skilled staff are available, they may be involved in managing your website and, therefore, may find it difficult to look at it afresh;
• An audit which uses in-house staff who are not accessibility specialists lacks the status of external, independent audit;

Self-audit alone is not recommended unless your organisation is large enough to provide skilled staff who have not been involved in operating the website and can maintain full objectivity in looking at it.

Self-audit is most useful as new content is being published to the website. It may not be practical to have new content audited externally on an on-going basis. Staff with responsibility for ensuring the accessibility of new content being published to the website should receive training in web accessibility and have access to appropriate tools and expert advice as required.

Automated auditing tools

Software can be very useful in testing website accessibility, but only up to a point. Most accessibility checkpoints cannot be verified by software alone. Of the 16 priority 1 checkpoints in WCAG 1.0, only one (12.1) can be verified automatically. All 15 others require human judgement.

For example, one of the WCAG checkpoints is to ensure that information does not rely on colour perception. Suppose you have an online appointment booking system on your site and it shows a calendar with available slots marked in green and unavailable slots in red. Some people with colour blindness cannot distinguish red from green so, unless it also shows the words "Available" and "Unavailable" or some suitable symbols, those people will not be able to tell which is which. An automated test might be able to tell that the colours red and green are used but not whether they are used for information purposes or whether additional methods are employed to give the same information. This requires human intelligence.

Automated auditing tools are best used by experts who can interpret their results accurately. In particular, auditors need to be able to quickly identify false positive and false negative results from the tools.

Software tools are more reliable in checking that a website is valid - that it conforms to standards for page markup- than for checking accessibility. Since valid markup is an important component of accessibility, software tools are useful for auditing this.

The WAI provides guidance on selecting web accessibility evaluation tools and also maintains an extensive list of such tools.