WhoCanUse is a dedicated web accessibility tool designed to bring attention and understanding to how specific color contrast combinations affect individuals with various visual impairments. Created and maintained by Corey Ginnivan, this platform seeks to humanize the data behind Web Content Accessibility Guidelines (WCAG) by demonstrating how design choices impact real users. Rather than relying solely on abstract grading systems, the tool allows designers and developers to see exactly how their color palettes appear to people with different types of color blindness, vision loss, and situational viewing conditions.

The tool functions by calculating the contrast ratio between two specified HEX color values, incorporating font size and font weight metrics to determine accessibility grades. By integrating specialized libraries like Chroma.js for contrast calculations and the Color-blind plugin for visual simulations, the platform generates a comprehensive report. This report illustrates how a chosen color scheme performs under various conditions, including protanomaly, deuteranopia, achromatopsia, cataracts, glaucoma, and situational factors like direct sunlight or night shift modes.

Some of the key features are:

• Color Contrast Analysis: Calculates precise contrast ratios based on input HEX codes for foreground and background elements.
• Visual Impairment Simulations: Provides side-by-side visual examples of how color combinations appear to users with various forms of color blindness.
• WCAG Grading: Assigns standardized accessibility grades based on contrast, text size, and font weight parameters.
• Custom Simulation Models: Includes custom-built simulations for conditions like cataracts, glaucoma, low vision, and situational lighting environments.
• Open Source Collaboration: Fully transparent codebase hosted on GitHub, allowing for community contributions and improvements.

The operation of WhoCanUse is straightforward and interactive. Users input their primary background and text colors using HEX values, along with font sizing and weight preferences. The interface immediately updates to show the resulting contrast ratio and provides a detailed breakdown of WCAG grades across a variety of demographic and medical scenarios. Each scenario includes percentage data on the affected population, sourced from recognized health and vision organizations, providing context for the importance of inclusive design.

Some common use cases include:

• UI Design Validation: Designers can verify that their brand color palettes meet accessibility standards before finalizing a design system.
• Inclusive Product Testing: Developers can identify which specific color combinations may cause visual strain for users with low vision or color blindness.
• Educational Accessibility Advocacy: Teams can use the tool to demonstrate to stakeholders why high-contrast choices are essential for creating an accessible digital experience.
• Situational Usability Testing: Practitioners can assess how environmental factors, such as bright direct sunlight, affect the readability of mobile application interfaces.