Accessibility evaluation

Accessibility evaluation

An accessibility evaluation is a method for ensuring that a digital interface can be successfully used by people with impaired vision, hearing, mobility, and/or thinking and understanding.

The evaluation is measured against, and ensures the interface adheres to, predefined accessibility standards.

It is most commonly performed against the Web Content Accessibility Guidelines (WCAG 2.1), which is an internationally recognised set of recommendations for improving web accessibility. All digital interfaces must meet the AA level standards and some are required to reach the level AAA. The WCAG 2.1 principles are grounded in the notion that a user interface must be perceivable, operable, understandable and robust at all times. They cover both the content and design of the interface, as well as the code behind it, and require input from all members of a project team.

Our Accessibility and Evaluation Approach

There are four methods for conducting accessibility evaluation that can be used alone or in combination with each other:

1. Evaluation

2. Usability testing

3. Assistive technology testing

1. Evaluation

This is a process of manually evaluating the interface against a list of standards (see checklist below) and is typically performed by experts on the interface content, design and development.

Accessibility checklist

The evaluation is completed against a list of predefined standards that reflect the key accessibility principles. See full list here: https://www.gov.uk/service-manual/helping-people-to-use-your-service/understanding-wcag.

 

Perceivable

Users must be able recognise and use the interface with the senses that are available to them.

  • Provide text alternatives (‘alt text’) for non-text content
  • Provide transcripts for audio and video
  • Provide captions for video
  • Make sure content is structured logically and can be navigated and read by a screen reader (this also helps if stylesheets are disabled)
  • Use the proper markup so the relationships between content are defined correctly
  • Do not use colour as the only way to communicate something
  • Use text colours that show up clearly against the background colour (contrast ratio of 4.5:1 for AA and 7:1 for AAA)
  • Ensure every feature can be used when text size is increased by 200% and that content reflows to a single column when it’s increased by 400%
  • Do not use images of text
  • Ensure the interface layout is responsive and adjusts based on the device, view post size, page orientation etc
  • Ensure the interface works well with assistive technologies and no content and functionality is lost

 

Operable

Users must be able to find and use your content, regardless of how they choose to access it (for example, using a keyboard or voice commands).

  • Make sure all functionality can be accessed by keyboard-only users
  • Let people play, pause and stop any moving content
  • Do no use blinking or flashing content – or let the user disable animations
  • Provide a ‘skip to content’ link
  • Use descriptive titles for pages and frames
  • Ensure users can move through content in a way that makes sense
  • Use descriptive links
  • Use meaningful headings and labels, making sure that any accessible labels match or closely resemble the label used in the interface
  • Enable ‘active focus’ for users using keyboard or assistive technology
  • Only use things like mouse events or dynamic interactions (like swiping or pinching) when they’re strictly necessary or let the user disable them and interact with the interface in a different way
  • Make it easy for users to disable and change shortcut keys

 

Understandable

Users must be able to understand the content and how the service works.

  • Use plain English
  • Keep sentences short
  • Explain all abbreviations and acronyms, unless they are well known and in common use
  • Make it clear what language the content is written in, and indicate if this changes
  • Ensure all form fields have visible and meaningful labels and are marked up properly
  • Make it easy for people to identify and correct errors in forms and other interactive elements

 

Robust

Ensure the content can be interpreted reliably by a wide variety of user agents (including reasonably outdated, current and anticipated browsers and assistive technologies).

  • Use valid HTML so user agents, including assistive technologies, can accurately interpret and parse content
  • Ensure your code lets assistive technologies know what every user interface component is for, what state it is currently in and if it changes
  • Ensure important status messages or modal dialogs are marked up in a way that informs user of their presence and purpose, and lets them interact with them using assistive technology
  • Lets the user return to what they were doing after they’ve interacted with the status message or modal input

2. Usability Testing

This process involves recruiting users with one or multiple disabilities and observing them performing a range of common tasks on the interface. Most usability testing sessions focus on users with impaired vision, hearing, mobility, and/or cognition who may or may not be using assistive technologies.

3. Assistive technology testing

This is a process of testing how well the interface can be used with a help of assistive technology, most commonly a screen reader. Unlike usability testing, this evaluation is perforated by an expert who typically does not have the disability. The goal is to assess the performance of the interface and identify potential pain points.