Accessibility is often described as a subset of inclusive design, which is accurate but understates the relationship. Accessibility focuses on compliance with standards and removal of specific barriers: does this meet WCAG 2.1 AA, can a screen reader navigate it, does the video have captions. These are binary questions with measurable answers. Inclusive design asks a broader question: who might use this and what conditions might they be experiencing, and how can the design serve all of them without requiring specialized accommodations?
The classic example of the relationship is the curb cut. Curb cuts were originally advocated for as an accessibility accommodation for wheelchair users. When they were implemented, it turned out they also benefited people with strollers, delivery workers with carts, cyclists dismounting, skateboarders, and elderly people with limited mobility. The accommodation designed for a specific disability produced a better experience for a much larger group of people. This is the pattern that inclusive design intentionally pursues from the beginning rather than discovering by accident.
Inclusive design considers dimensions of difference beyond disability. Age: does this work for someone with age-related vision changes or limited technology experience? Language: does this work for someone whose primary language is not English? Situational context: does this work for someone reading in bright sunlight on a phone, or in a noisy environment, or in a moment of stress or time pressure? Digital literacy: does this work for someone who is not comfortable with technology interfaces? Each of these considerations produces design decisions that make the product better for the specific group and often for everyone.
The business case for inclusive design is straightforward and underappreciated. In the United States, approximately sixty-one million adults have some form of disability. An additional large population has situational impairments, low bandwidth connections, older devices, or language barriers. A product designed inclusively from the start reaches all of these users without modification. A product designed for an assumed ideal user and then retrofitted for everyone else is more expensive to build, less coherent in its experience, and frequently still inadequate for the people it was not designed with in mind.
Inclusive design in practice begins with a simple commitment: before designing anything, ask who might use this and under what conditions. The answer is almost always a wider range of people in a wider range of circumstances than the person doing the designing initially imagined. Bringing that wider range into consideration before decisions are made, rather than after the design is complete, produces better outcomes for everyone without the cost and awkwardness of accommodation added as an afterthought.
The goal of inclusive design is not to make something that tries to please everyone and therefore pleases no one. It is to make something whose primary design decisions were informed by the full range of people who will use it, producing an experience that works well for most of them without requiring any of them to use a separate, lesser version.