Charts are a powerful way to visualize data and communicate insights on the web. But how do you make sure your charts are fast, accessible, and responsive to different devices and screen sizes? In this article, you'll learn some tips and best practices for optimizing your chart data sources for web performance and accessibility.
The first step to optimize your chart data sources is to choose the right data format for your needs. There are many options available, such as CSV, JSON, XML, or binary formats like Protobuf or Avro. Each format has its own advantages and disadvantages in terms of size, readability, structure, and compatibility. Generally, you want to use a format that is compact, easy to parse, and supported by your charting library and web browser. For example, JSON is a popular choice for web applications because it is lightweight, human-readable, and widely supported.
The ideal data format would encompass all the necessary metrics and dimensions, and, more importantly, seamlessly integrate into a workflow for ingestion and normalization. In my profesional experience, prioritizing the selection of a compact and easily parseable format aligns with the objective of enhancing data workflows.
In order to optimize your chart data sources, it is important to reduce the data size. Large data sets can take up more bandwidth, slow down web page loading time, and negatively impact user experience. To shrink the data size, you can use techniques such as filtering out unnecessary or irrelevant data, aggregating and summarizing by categories or dimensions, sampling a representative subset of the data to display, and compressing the data file with an algorithm or tool.
Optimizing your chart data sources involves using web performance techniques such as caching, CDN, HTTP/2, and preloading. Caching stores data on the server or browser cache to reduce repeated requests and improve loading speed. CDN distributes data across multiple servers and locations to reduce latency and network congestion. HTTP/2 enables multiplexing, compression, and prioritization of requests and responses. Preloading uses the <link rel="preload"> tag to instruct the browser to fetch your data in advance and enhance perceived performance.
To optimize your chart data sources and make them responsive to different devices and screen sizes, you can use media queries, viewport units, scalable vector graphics (SVG), or flexbox or grid layout. Media queries allow you to apply different styles and properties to your charts based on the screen width, height, orientation, or resolution. Viewport units size your charts relative to the viewport dimensions. SVG creates resolution-independent charts that can scale up or down without losing quality or clarity. Lastly, flexbox or grid layout arranges your charts in a flexible and responsive way.
Making charts responsive is also a requirement for making them accessible. This ensures that users can view the chart at a natural scale and orientation for their device.
To make your charts accessible for all users, including those with disabilities or impairments, you can use ARIA attributes and roles to add semantic information and context, such as labels and descriptions. Additionally, you can use the alt attribute to provide a text alternative for your charts, as well as captions or subtitles for any audio or video elements. Furthermore, it’s essential that your charts are keyboard-accessible and can be navigated using the tab, arrow, enter, or space keys.
To optimize your chart data sources, the last step is to test and measure the performance and accessibility of your charts. This includes using web performance tools like Lighthouse, WebPageTest, or PageSpeed Insights to analyze and improve the speed, efficiency, and usability of your web page and charts. Additionally, accessibility tools such as axe, WAVE, or ChromeVox can be used to evaluate and enhance the accessibility and compliance of your web page and charts. Finally, user feedback from surveys, interviews, or analytics can help you understand how users interact with and perceive your charts.