How can you make your Shiny app accessible to all users?

1 Use semantic HTML

HTML is the language that defines the structure and content of your web page. Semantic HTML means that you use the appropriate tags and attributes to describe the meaning and purpose of each element, rather than just the appearance. For example, use <h1> to <h6> tags for headings, <p> for paragraphs, <ul> and <ol> for lists, and <table> for tables. Semantic HTML helps screen readers and other assistive technologies to understand and navigate your page, and also improves the SEO and performance of your app.

2 Add alt text and captions

Images, graphs, and videos can enhance your data visualization, but they can also exclude users who cannot see or hear them. To make your visual elements accessible, you need to provide alternative text and captions that describe their content and function. Alternative text is a short text that appears when an image cannot be loaded or is read by a screen reader. Captions are text that accompanies a video or audio file and transcribes the speech and sounds. You can add alt text and captions to your Shiny app using the alt and caption arguments of the renderImage, renderPlot, and renderVideo functions.

3 Use color contrast and labels

Color can be a powerful tool to convey information and emotions in your data visualization, but it can also create problems for users who have color blindness or low vision. To make your color choices accessible, you need to ensure that they have enough contrast with the background and with each other, so that the text and data points are readable and distinguishable. You can use online tools like WebAIM Color Contrast Checker to test your color contrast ratios. You also need to provide labels or legends that explain the meaning of each color, and avoid relying on color alone to convey information.

4 Make your app responsive and keyboard-friendly

Your Shiny app should be able to adapt to different screen sizes and resolutions, so that users can access it from any device, such as a desktop, laptop, tablet, or smartphone. A responsive app adjusts the layout and content of your page according to the available space and orientation, using CSS media queries and Bootstrap grids. A responsive app also ensures that your data visualization is not distorted or cropped, and that the text and buttons are not too small or too large. Additionally, your app should be keyboard-friendly, meaning that users can navigate and interact with your app using only the keyboard, without using the mouse or touch screen. You can make your app keyboard-friendly by using the tabindex, role, and aria attributes in your HTML elements, and by providing visual feedback for the keyboard focus.

5 Test and validate your app

The final step to make your Shiny app accessible is to test and validate it using various tools and methods. Doing so can help you identify and fix any accessibility issues or errors that you might have missed. You can use Web Content Accessibility Guidelines (WCAG) as a set of standards to follow, WAVE as an evaluation tool, Lighthouse to audit performance, accessibility, SEO, and best practices, and manual testing for user experience. Making your Shiny app accessible to all users is a rewarding experience that is not only good practice, but also creates an inclusive, user-friendly, and engaging app for everyone. Following these tips and best practices will ensure your success.