Accessibility means building software that people with disabilities can actually use, those who rely on screen readers, cannot use a mouse, have low vision, or process information differently. It is often treated as an afterthought, which is both a design failure and, increasingly, a legal and commercial risk.
The Web Content Accessibility Guidelines, or WCAG, are the widely recognized standard for accessibility, organized around principles that content should be perceivable, operable, understandable, and robust. They cover concrete things: sufficient color contrast, text alternatives for images, keyboard navigation, labels that screen readers can announce, and content that does not rely on a single sense. Conformance is measured in levels, with AA being the common target.
Practically, a large share of people have some disability, and inaccessible software simply excludes them, which is both wrong and a loss of customers. Legally, accessibility requirements increasingly apply to digital products, and inaccessible apps have drawn complaints and lawsuits. Commercially, accessible design tends to be better design for everyone: clearer, more navigable, more robust across devices.
Like security, accessibility is far cheaper and better when designed in from the start than retrofitted at the end. That means considering it in design, building with accessible components, and testing with real assistive technology, not just automated checkers. Software that everyone can use is simply higher-quality software, which is why we build toward it rather than around it.
Everyone can use it, or it is not finished.
This is general educational information about building software, not specific technical or business advice.