Progressive Enhancement

Progressive enhancement means building so the core content and functions work with minimal technology, then layering on improvements for capable browsers — rather than requiring everything to work before anything does.

In practice: a form that submits without JavaScript and gets nicer with it; content in the HTML rather than fetched after load. The payoff shows up on slow connections, older devices and for search crawlers, all of which see the base layer.

It matters for SEO because content requiring JavaScript execution to appear is indexed less reliably and more slowly than content present in the initial HTML.

Why it matters

A site where nothing renders until a large JavaScript bundle loads is slow for real users on real phones, and harder for search engines to index — two problems with one cause.

Related terms

SSR, SSG and ISRThree ways of producing a web page: server-side rendering builds it per request, static site generation builds it once at deploy time, and incremental…Core Web VitalsCore Web Vitals are Google's three measures of page experience: Largest Contentful Paint (loading), Interaction to Next Paint (responsiveness) and Cum…Crawl BudgetCrawl budget is how much crawling a search engine will do on your site in a given period. It becomes a real constraint on large sites, where wasted cr…

More in Web & Performance

Core Web VitalsLargest Contentful Paint (LCP)Cumulative Layout Shift (CLS)Time to First Byte (TTFB)SSR, SSG and ISRCDN (Content Delivery Network)Headless CMSWeb ApplicationTechnical Debt

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