In any type of software development, modularity is king when it comes to building maintainable code (if coding isn't your thing, you can use a website builder instead). As a result, you’ll want to keep a close eye on Web Components. Browser support isn’t great, but if you grab yourself some polyfills, you can get ahead of the curve and start taking advantage of custom elements to structure your code right away. This style of development is the future, so it’s worth getting familiar with it now.
HTML5 itself introduced a number of new elements (and deprecated several) to help encourage good coding practices. You may have heard of semantic markup, which refers to the use of HTML5’s descriptive elements such as <article> and <figure> to indicate the type of content they contain.
This can really help with the cleanliness of your code, as the HTML elements will immediately identify, for example, which parts represent the menu bar, your sections of content, the footer and so on.
01. Recognise and synthesise speech
These would once have been complex functions requiring specialised software, but they’re now being built directly into browsers. The Web Speech API has components which support text-to-speech and speech-to-text. The latter of these will either use an online service (Chrome uses the Google Cloud Speech API) or the device’s native speech recognition service. Expect to see this being used widely on mobile devices in the future.
02. Display a colour picker
Trivial as it may sound, this is a great example of how HTML5 is simplifying common tasks which would previously have required custom coding of a fairly complex UI component. <input type="color"> will display a visual colour picker when clicked, using a colour picker native to the device. This could be particularly useful with HTML canvas. It’s widely supported with the exception of Safari on mobile.
03. Recolour the browser UI
This can offer a nice aesthetic touch on mobile platforms. <meta name="theme-color" content="#FFFFFF" /> is designed to instruct the browser to recolour the toolbar when viewing your site. Unfortunately, it’s a little non-standardised, so while "theme-color" works with Chrome, Firefox and Opera, on iOS you’ll need "apple-mobile-web-app-status-bar-style" (only works in fullscreen mode).
04. Different images for different screens
Hopefully you’re already implementing responsive design, in which case your images will be resizing to suit the viewport. This isn’t perfect, since you’ll be forcing the user to download the largest version of the image then downsampling it. Enter the HTML5 <picture> element, which enables you to specify different images to be displayed depending on the screen resolution the site is being viewed on.
05. Vibrate your phone
The unambiguously named Vibration API exposes a single function, vibrate(), which will do exactly what it says on devices which support it. The function takes a list describing a vibration pattern as its argument. It’ll work on Chrome, Firefox and Opera, although you’re out of luck on Edge or Safari. It’s reported that some ads are using this to attract the user’s attention, so the jury’s out on whether it’s actually a good idea.