Progressive rendering is a technique used in web development to improve the loading time and user experience of a web page. The idea behind progressive rendering is to display the content of a web page as soon as possible, even before all the resources (such as images, videos, scripts, etc.) have finished loading.
One way to achieve progressive rendering in HTML is by using the defer and async attributes on script tags. These attributes can be used to tell the browser to load and execute scripts in a way that doesn't block the rendering of the rest of the page. For example, using the defer attribute on a script tag will cause the browser to load the script in the background and execute it only after the page has finished loading.
Another way to achieve progressive rendering is by using the HTML loading attribute. The loading attribute can be used on the img and iframe elements to indicate whether the resources should be loaded lazily or eagerly. For example, setting the loading="lazy" on an image tag tells the browser to only load the image when it comes into view, this will greatly improve the loading time of the web page.
Additionally, to improve the progressive rendering, you can use techniques such as lazy loading, which is the process of loading resources only when they are needed. This technique can be used to load images and videos only when the user scrolls to them, for example. This helps to reduce the amount of data that needs to be loaded initially, improving the loading time of the web page.
In summary, Progressive rendering is a technique that allows a web page to be rendered and displayed as quickly as possible, improving the user experience and loading time. Techniques such as using the defer, async and loading attributes on script tags, and using lazy loading can greatly help in achieving progressive rendering in HTML.