Hi all,
There are some older posts about this circa 2018/2019 but it seems like there hasn't been any progress with PWA. For HTML5 games, PWA provides a way to give our players an optimal experience on their device by letting them install our games as an app that will support fullscreen properly among other features. PWA is supported on iOS, Android, Windows, ChromeOS etc. For basic web games, this is as simple as adding a manifest.json to your zip bundle and an icon that will be displayed on the homescreen and system menus.
Anyway, PWA isn't fully supported out of the box on itch unfortunately. The manifest.json appears to get stripped when the game is loaded in the iframe. However, a workaround is to link your players who want PWA to the itch zone page directly, which will then load the manifest correctly, although I'm not sure how stable the zone page link is . Example game here and the corresponding zone page. On the zone page, on your iPhone you can Share -> Add to homescreen, on Android, and in the Chrome browser on PCs etc the option to install should be in the URL bar. But it would be great if itch could support that feature directly from the game page itself.
Thanks!