Installed web apps each keep their own browser profile

Installing a site as an app from Chrome, Edge or Safari produces something that looks like an application and behaves like a browser profile. It has its own cache, its own site storage and its own service worker, separate from the browser you installed it from.

Where they store data

du -sh ~/Applications/Chrome\ Apps.localized/* 2>/dev/null
du -sh ~/Library/Application\ Support/Google/Chrome/Default/Web\ Applications \
  2>/dev/null
du -sh ~/Library/Containers/*.webapp* 2>/dev/null | sort -h

Chromium based web apps store inside the parent browser's profile, under a Web Applications folder, while Safari web apps get their own container. Either way the storage is not shared with the browser's normal browsing data, which is why clearing browsing data does not affect them.

Why they grow

• Offline data. A web app that works offline stores what it needs to, without a size limit you can see.
• Service workers. Each app registers its own, with its own cache.
• Media. Anything the app downloads for offline use, which for a music or document app is substantial.
• Duplication. The same site used in the browser and as an app stores its data twice.

Clearing one

Removing the web app removes its storage, which is the cleanest route. Inside a Chromium web app there is also a settings path to site data, and Safari web apps appear in Safari's website data list under their own entry.

Worth knowing before installing several

Each installed web app is a full profile, so a Mac with six of them is running six profiles' worth of cache and site storage. On a small drive that is a real cost for what feels like a shortcut, and it is the same structure covered in what every Chromium browser stores.