The principle of accessibility is the concept that every design should be usable by as many people as possible, without any modification.
Historically, accessibility in design focused on accommodating people with disabilities. Nowadays, accessible design has evolved to benefit everyone.
There are four characteristics of accessible designs:
- Perceptibility — Everyone can perceive your design, regardless of sensory abilities. To improve perceptibility: present information using redundant coding methods (textual, iconic, and tactile), provide compatibility with assistive sensory technologies (use ALT tags for your images, and position controls and information in an organised ways that users can perceive them without challenge.
- Operability is when everyone can use your design, no matter their physical abilities. To improve operability: minimise repetitive actions and the need of continuous physical effort, facilitate use of controls through appropriate constraints, provide compatibility with assistive physical technologies, and accessible controls and information.
- Simplicity is when everyone can understand and use your design, regardless of experience, literacy, or concentration level. To improve simplicity: remove unnecessary complexity, have clear and consistent labels and modes of operation, use dynamic design to present only relevant information and controls, provide clear prompt and feedback for all actions, and ensure the level of language accommodates a diverse range of literacy
- Forgiveness is when your design minimises the chances of errors. To improve forgiveness: design controls that can only be used the correct way to prevent errors, use confirmations and warnings to reduce the occurrence of errors, and include reversible actions and safety nets such as the ability to undo an action.