Definition
A progressive web app (PWA) is a website built with standard web technologies that can also behave like an installed app: it can be added to a device's home screen or app launcher, open in its own window, work offline or on poor connections, and send push notifications. The term was coined in 2015, and PWAs are supported to varying degrees by Chrome, Edge, Safari and Firefox.
Three pieces make a site a PWA. A web app manifest, a JSON file, describes the app's name, icons, start URL and display mode. A service worker, a script that runs separately from the page, intercepts network requests so the app can cache assets and content for offline use and receive push messages. And the site must be served over HTTPS. Browser support has widened over time. Apple added web push for home-screen web apps in iOS 16.4 in 2023, and desktop Chrome and Edge let users install PWAs from the address bar.
The tooling around PWAs has also changed. Lighthouse 12, which reached PageSpeed Insights on May 10, 2024, removed the PWA category after Chrome updated its installability criteria, and Chrome now directs developers to its own PWA documentation for testing (Lighthouse release notes). There is no PWA score in Lighthouse any more, and no PWA-specific ranking benefit in Google Search.
For search, Google treats a PWA like any other JavaScript-heavy website. It is indexed page by page, so each piece of content needs its own URL, internal links need to be real <a href> links, and content has to be present after rendering. The common risk is the app shell pattern, where the server sends a minimal HTML shell and JavaScript fetches and renders everything else. Googlebot can usually render that, with some delay, but other crawlers often cannot.
That gap matters more in AI search. Vercel's December 2024 analysis of AI crawler traffic found that OpenAI's crawlers, ClaudeBot, Meta's and Perplexity's crawlers do not execute JavaScript, while Google's Gemini uses Googlebot's rendering (Vercel). A PWA that renders its content only in the browser may be fully indexed in Google yet look empty to the crawlers behind ChatGPT search, Claude and Perplexity, and therefore never be cited there.
The fix keeps the app-like benefits while making content visible to every crawler. Render important content on the server, either with server-side rendering or static generation, and let the service worker and client-side code add offline support and interactivity on top. Give every product, article or listing a stable, crawlable URL with its main text, title and structured data in the initial HTML. Avoid serving crawlers a cached offline page or an 'install our app' interstitial instead of the content. Then check the raw HTML your server returns, for example with a plain HTTP request, and confirm in AI crawler logs that AI user agents receive full pages. Speed still matters too: PWAs that ship large JavaScript bundles often struggle with Core Web Vitals, especially Interaction to Next Paint. See JavaScript rendering and mobile-first indexing for the underlying crawl behavior.
Examples of Progressive Web Apps (PWA)
- A grocery delivery PWA renders its product catalog entirely in the browser. Google indexes the products after rendering, but none of them appear in ChatGPT search answers until the team adds server-side rendering for product pages.
- A news publisher's PWA uses a service worker to cache articles for offline reading on commuter trains, while still serving each article as server-rendered HTML at its own URL.
- A travel booking site removes an 'install our app' full-screen prompt that appeared on first visit, after finding that AI crawlers were receiving the prompt markup instead of the destination guide content.
- A team auditing an older PWA finds its internal navigation uses click handlers instead of real links, so crawlers could not discover most pages, and replaces them with standard anchor tags.
