Test your website's accessibility with our free online color blindness simulator. Apply real-time SVG filters to preview how users with CVD perceive your design.
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Technical Specification: Free Online Color Blindness Simulator
Overview
A high-performance, browser-based accessibility tool that allows users to input a URL or upload an image to preview how it appears to individuals with various forms of Color Vision Deficiency (CVD).
Core Features
- Real-time SVG Filter Engine: Toggle between Protanopia, Deuteranopia, Tritanopia, and Achromatopsia filters.
- Side-by-Side Comparison: View the original image/preview next to the filtered version.
- Contrast Analysis Overlay: A toggleable grid that highlights low-contrast areas based on luminosity.
- Responsive Preview Window: A sandboxed iframe area that maintains aspect ratio across mobile and desktop viewports.
- Export Functionality: Download the filtered preview as a PNG for accessibility documentation.
UI Layout
- Header: Clean, professional title with a brief "How to use" tooltip.
- Control Panel: A sticky top bar containing the URL input field, filter selection dropdown, and action buttons (Reset, Download).
- Main Workspace: A split-screen layout. Left side displays the original content; right side displays the filtered simulation.
- Status Bar: Displays current filter mode and accessibility compliance hints.
Design & Aesthetics
- Color Palette: Professional light-mode palette using
#FFFFFF(background),#F8FAFC(secondary background),#334155(text), and#2563EB(primary action blue). - Typography: Inter or system-ui sans-serif stack for maximum readability.
- Animations:
- Smooth
opacitytransitions when switching filters. - Subtle
box-shadowlift on hover for buttons. - Micro-interactions on toggle switches using CSS
transform.
- Smooth
Technical Constraints & Directives
- Single File: All CSS and JS must be embedded within the single HTML file.
- No Persistence: Do not use
localStorage,sessionStorage, or cookies. All state must be held in JavaScript variables. - Iframe Compatibility: The app must function within a sandboxed iframe. Ensure all external resources (like fonts) are loaded via HTTPS.
- No Popups: Use custom
<div>based modals for alerts or instructions. - Performance: Use
requestAnimationFramefor filter updates to ensure 60fps performance during interaction.
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Files being used
Frequently Asked Questions
Everything you need to know about using this application.
What is a color blindness simulator and why is it important?
A color blindness simulator is a diagnostic tool that applies mathematical filters to visual content to mimic how individuals with Color Vision Deficiency (CVD) perceive colors. By transforming the color spectrum, developers can identify areas of a design that lack sufficient contrast or rely too heavily on color-coding. Ensuring your digital content is accessible to users with protanopia, deuteranopia, or tritanopia is a critical component of inclusive web design. This tool helps you verify that your information remains legible and functional for all users, regardless of their visual capabilities.
How do SVG filters work in this accessibility tool?
This tool utilizes SVG feColorMatrix filters to manipulate the RGB color channels of the webpage preview. By applying specific transformation matrices, we can accurately simulate the loss of red, green, or blue light sensitivity that characterizes different types of color blindness. Because these filters are applied at the browser level using standard web technologies, they provide a highly accurate representation of color perception shifts. This allows designers to make data-driven adjustments to their color palettes to improve overall user experience.
Does this tool save my data or website previews?
No, this application is built with a strict privacy-first architecture. It operates entirely within your browser's memory and does not utilize local storage, cookies, or server-side databases to save your inputs or previewed content. Once you close the browser tab or refresh the page, all session data is immediately purged. This ensures that your design work remains confidential and secure, as no information is transmitted to or stored on any external servers.
How can I improve my website's accessibility after testing?
After identifying problematic color combinations using the simulator, you should focus on increasing contrast ratios between text and background elements. Aim to meet WCAG 2.1 AA or AAA standards by using tools that calculate luminosity contrast rather than relying on color alone. Additionally, consider using secondary visual cues such as patterns, textures, or icons to convey information. By decoupling meaning from color, you create a more robust interface that is inherently more accessible to all users, including those with full color vision.
