Progressive enhancement describes a method in web design that includes accessibility, semantic markup and separation of information and presentation in order to make a website usable for devices that only have limited functions. This also speeds up the loading process by instantly transferring text content through the HTML source code instead of waiting for JavaScript to execute, making it easier for web search engines to index and improving backward compatibility with web browsers.
The philosophy behind this is that, in principle, web pages should be accessible with any web browser (including text-based) and any type of Internet connection in its most basic form – the provision of information – and that users with better bandwidth and more advanced browsers with advanced functionality should be presented with an improved version of the site.
Progressive enhancement is the reversal of the practice of graceful degradation that was previously prevalent in web development, where a web page was initially programmed for the most modern devices, and an alternative version was provided for older devices that did not support modern features, or the newer features were simply relied upon to be ignored, and a more basic version is automatically displayed. The problem with this approach, however, is that either the workload is higher, because several different versions of a page have to be programmed and maintained for different devices, or that an older device does not have the desired fault tolerance and the content is therefore not displayed or only insufficiently displayed or usable.
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This attitude and approach on the part of many web designers resulted from the fact that early browsers were hardly standardized with regard to the support of HTML, CSS and JavaScript and that websites were hardly displayed on devices other than regular computer browsers, since e.g. mobile devices (PDA/smartphone)) did not yet have the ability to display websites or even connect to the internet. In practice, the theory of “dignified downgrading” has been supported by the view that the end user simply needs to update their browser software. However, this attitude ignores the fact that many users cannot easily update their software because, for example, company computers have limited access rights and software is not constantly updated there. It also ignores the fact that there are users who either intentionally do not update or who connect via mobile devices that have limited bandwidth and support for images and scripts, or screen size.
This is met by progressive enhancement by making the basic information that makes up a website accessible to all devices and providing extended functionality to those devices that have the technical capabilities to use it by means of externally integrated style sheets and/or scripts.
