Introduction to Web Accessibility
Web accessibility means building websites that everyone can use — including the more than 1 billion people worldwide living with a disability.
What is Web Accessibility?
Web accessibility is the practice of designing and developing websites, tools, and technologies so that people with disabilities can perceive, understand, navigate, and interact with them — and contribute to the web.
Disabilities that affect how people use the web include:
The international standard for web accessibility is the Web Content Accessibility Guidelines (WCAG) 2.2, published by the World Wide Web Consortium (W3C). WCAG 2.2 provides testable success criteria organized around four core principles.
Why Accessibility Matters
It's a Human Right
The UN Convention on the Rights of Persons with Disabilities recognizes access to information technology as a human right. The web has become essential infrastructure — for education, employment, healthcare, and civic life.
Legal Requirement
The ADA, Section 508, the European Accessibility Act, and similar laws worldwide require accessible digital experiences. Non-compliance carries legal risk and financial penalties.
Business Value
People with disabilities represent a market of over $490 billion in disposable income in the US alone. Accessible sites reach more customers, have better SEO, and convert better across all user groups.
Better for Everyone
Accessibility improvements benefit everyone. Captions help people in noisy environments. Good color contrast helps people in bright sunlight. Keyboard navigation helps power users. This is the "curb cut effect" — features designed for disability improve experience for all.
Who Benefits?
Accessibility benefits go far beyond people with permanent disabilities. Consider these scenarios:
A person with low vision who uses screen magnification to read small text
Also helps: anyone reading on a small screen
A deaf user who relies on captions to understand video content
Also helps: someone watching in a noisy coffee shop
A user with motor impairment who navigates exclusively with a keyboard
Also helps: power users and developers who prefer keyboard shortcuts
Someone with dyslexia who benefits from clear headings and plain language
Also helps: non-native speakers and users in a hurry
An older adult with age-related decline in vision, hearing, and dexterity
Also helps: anyone using a device in poor lighting
A user with temporary injury (broken arm) who can only use one hand
Also helps: parents holding a baby while browsing
The Four POUR Principles
WCAG 2.2 is organized around four foundational principles, known by the acronym POUR. Any website that fails to meet any of these principles is considered inaccessible.
P — Perceivable
Information and user interface components must be presentable to users in ways they can perceive. Content cannot be invisible to all of a user's senses.
Examples: Alt text for images, captions for videos, sufficient color contrast, content that doesn't rely solely on color to convey meaning.
O — Operable
User interface components and navigation must be operable. Users must be able to operate the interface — it cannot require interaction that a user cannot perform.
Examples: Full keyboard accessibility, no keyboard traps, no time limits that cannot be extended, no content that flashes more than three times per second.
U — Understandable
Information and the operation of user interface must be understandable. Users must be able to understand the information as well as how to operate the user interface.
Examples: Page language declared in HTML, consistent navigation, error messages that explain what went wrong and how to fix it, labels for all form inputs.
R — Robust
Content must be robust enough to be interpreted by a wide variety of user agents, including assistive technologies. As technologies evolve, the content should remain accessible.
Examples: Valid, well-structured HTML, ARIA used correctly, name/role/value exposed for all UI components, status messages announced to screen readers.
Getting Started
Starting your accessibility journey can feel overwhelming, but you don't need to fix everything at once. Here are practical first steps:
Run an automated scan
Install the WAVE or axe browser extension and run it on your homepage. Fix all the errors it identifies — these are reliable, high-confidence issues.
Test with just your keyboard
Unplug your mouse and try to use your website. Can you navigate menus? Open dropdowns? Submit forms? Complete a purchase? If not, keyboard users can't either.
Check color contrast
Use the WebAIM Contrast Checker or browser DevTools to verify that all text meets 4.5:1 contrast ratio against its background. This is one of the most common failures.
Audit your images
Review every image on your site. Add descriptive alt text to meaningful images. Use alt="" for decorative ones. Think about what a screen reader user would need to understand the image's purpose.
Next Steps
Ready to go deeper? Explore our other guides:
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