How do you ensure HTML5 works across all devices?

1 Use responsive design

Responsive design is a technique that enables web pages to adjust to different screen sizes and orientations, using flexible layouts, media queries, and images. This provides visitors with a consistent and user-friendly experience regardless of the device they use. To use responsive design, you must set the viewport meta tag in the HTML document head section in order to control how your page is scaled and rendered. Additionally, you should also use relative units such as percentages, ems, or rems instead of absolute units such as pixels for your layout and typography. Media queries can be employed to apply different styles based on the device width, height, orientation, resolution, or other features. Finally, flexible images that are able to resize or crop according to the available space can be used; alternatively, you can also use different image sources for different devices using the srcset and sizes attributes or the picture element.

2 Validate your code

Validating your code means checking it for errors and compliance with the HTML5 standards and specifications. This can help you avoid compatibility issues, improve performance, and enhance accessibility and SEO. To validate your code, you can use online tools, such as the W3C Markup Validation Service, or browser extensions, such as HTML Validator. You can also use the doctype declaration at the beginning of your HTML document to specify that you are using HTML5 and help the browser render your page correctly.

3 Test your page on different devices and browsers

Testing your page on different devices and browsers is essential to ensure that your HTML5 features work as expected and that your page looks and functions properly. You can use device emulators or simulators on your computer to mimic the behavior and appearance of different devices and browsers. Remote debugging tools allow you to inspect and modify your page on a real device connected to your computer via USB or Wi-Fi. Cross-browser testing tools enable you to run your page on multiple browsers and platforms in the cloud, while user feedback tools allow you to collect data from real users who visit your page on different devices and browsers. All of these methods and tools can help you generate screenshots or reports of the results.

4 Use fallbacks and polyfills

Fallbacks and polyfills are techniques that allow you to provide alternative solutions or enhancements for HTML5 features that are not supported by some devices or browsers. For example, you can use fallback content or messages for HTML5 elements or attributes that are not recognized by some browsers, such as video , audio , or canvas . Additionally, you can use polyfills, which are scripts or libraries that emulate or add missing HTML5 features or APIs, such as localStorage , geolocation , or fetch . To ensure that a device or browser supports a specific HTML5 feature or API before using it, you can employ feature detection. This method involves using native JavaScript methods, such as in or typeof , or third-party libraries, such as Modernizr. If needed, fallbacks or polyfills can be applied after the feature detection.

5 Follow security best practices

Security is an essential element of any web page, especially when HTML5 features involving user data, communication, or storage are used. To protect your page and your users from malicious attacks, it is advised to adhere to several security best practices. HTTPS, a protocol that encrypts the data exchanged between your server and your users' browsers, should be employed to prevent eavesdropping, tampering, or impersonation. A free SSL certificate can be obtained from services such as Let's Encrypt or Cloudflare. The Content-Security-Policy meta tag or HTTP header should be used to specify which sources of content are allowed or blocked on your page, such as scripts, images, stylesheets, or fonts. This will help prevent cross-site scripting (XSS) or injection attacks. The Subresource Integrity attribute can be employed to verify the integrity of external resources loaded on your page and thereby prevent compromised or malicious resources from affecting the page's functionality or security. Lastly, the sandbox attribute should be used to restrict the behavior and access of iframe elements embedded on your page. This will help isolate potentially harmful or untrusted content from your page's context and prevent cross-site request forgery (CSRF) or clickjacking attacks.

6 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?