The Four Principles of Accessibility (POUR)
Estimated read time: 6–7 minutes
Introduction: Why POUR Matters
Welcome back to our series on web accessibility! In our last post, we explored what WCAG is and why it’s essential for everyone. Now, let’s break down the heart of WCAG: the four principles that make digital content accessible to all.
These principles—Perceivable, Operable, Understandable, and Robust (POUR)—are the foundation of accessible design. If your website or app meets these, you’re well on your way to true inclusivity.
1. Perceivable: Information Must Be Presentable to All Senses
Definition: Users must be able to perceive the information being presented (it can’t be invisible to all their senses).
Examples:
- Provide text alternatives (alt text) for images so screen readers can describe them.
- Offer captions and transcripts for audio and video content.
- Use sufficient color contrast for text and backgrounds.
Quick Tips:
- Don’t rely on color alone to convey meaning.
- Structure content with headings and lists for clarity.
- Make sure all non-text content has a text equivalent.
2. Operable: User Interface Components Must Be Usable
Definition: Users must be able to operate the interface (the interface cannot require interaction that a user cannot perform).
Examples:
- All functionality is available via keyboard (not just mouse).
- Provide clear focus indicators for interactive elements.
- Avoid content that flashes rapidly (to prevent seizures).
Quick Tips:
- Test your site with only a keyboard—can you access everything?
- Ensure navigation is consistent and logical.
- Give users enough time to read and use content.
3. Understandable: Content and Operation Must Be Clear
Definition: Users must be able to understand the information and how to use the interface.
Examples:
- Use clear, simple language and instructions.
- Label form fields and buttons meaningfully.
- Provide helpful error messages and guidance.
Quick Tips:
- Avoid jargon and unexplained abbreviations.
- Keep navigation and layout predictable.
- Make error messages specific and actionable.
4. Robust: Content Must Be Compatible with Current and Future Tools
Definition: Content must be robust enough to be interpreted reliably by a wide variety of user agents, including assistive technologies.
Examples:
- Use valid, semantic HTML.
- Ensure ARIA roles and attributes are used correctly.
- Test with different browsers and assistive tech (like screen readers).
Quick Tips:
- Regularly validate your code for errors.
- Stay updated with evolving web standards.
- Avoid relying on features that only work in one browser or device.
Summary: POUR in Practice
When you design with POUR in mind, you’re not just checking boxes—you’re making the web better for everyone. Start with small changes, and you’ll see big improvements in usability and inclusion.
Next Up:
In our next post, we’ll demystify the WCAG conformance levels (A, AA, AAA) and what they mean for your projects.
Let’s keep building a more accessible web—one principle at a time!