What is a PWA? A plain-language guide for iPhone users

A PWA, short for progressive web app, is a website built so that a browser can install it and run it much like an app. Once installed it has its own icon on your home screen, opens in its own window instead of a Safari tab, can keep some things working when you are offline and, on an iPhone, can send notifications if you allow it. Nothing is downloaded from the App Store. It is still the website, shown by the browser's engine, which is why it behaves like an app in some ways and like a website in others. This guide explains the term, how you get one onto an iPhone, and what it can and cannot do.

What makes a website a PWA?

Two small additions to an ordinary website do most of the work. You never see either directly, but between them they explain most of how an installed web app behaves.

A manifest. A short file that tells the browser the app's name, its icon, the colors to show around it and the page it should start on. MDN, Mozilla's web documentation, describes the manifest as the information a browser needs to install a web app, and says every PWA must have one. When a site you add to the home screen arrives with a proper icon and a sensible name rather than a tiny picture of the page, that is the manifest at work.

A service worker. A small script the browser runs in the background for that one site. It can keep copies of pages and files on your phone so that parts of the app open without a connection, and it is the piece that receives push notifications. MDN notes that a PWA does not strictly need one to be installable, but most have one so that at least something works offline.

Everything else is the website you already know. There is no separate app version of the code: the same address serves the page in a Safari tab and inside the installed app. The word progressive simply means the site works as an ordinary page everywhere and adds these extras wherever the browser supports them.

How do you get a PWA on an iPhone?

Apple's own guide describes the flow in Safari: open the site, tap the Share button, scroll the list of options and choose Add to Home Screen, check that Open as Web App is turned on, then tap Add. An icon appears on your home screen, and Apple says that tapping it opens the website "just like an app". If Add to Home Screen is missing from the list, the guide explains how to add it back through Edit Actions at the bottom of the same menu.

Menus change between iOS versions, so if what you see doesn't match, Add a website to your iPhone home screen: setup and fixes works through the common differences and what to do about them.

There is no App Store step, no review and nothing to download in advance. You can add almost any website this way; a site built as a PWA is simply the one designed to behave like an app once it opens.

What can a PWA do on an iPhone, and what can't it?

The honest picture is mixed. The last column says who documents each point; the sources are listed at the end.

The pattern to remember: a PWA is a website with app manners. It borrows the icon, the window and the notifications. It does not gain a native app's reach into the phone, and what it stores on your phone stays there only as long as the browser lets it.

PWA, bookmark or App Store app: what's the difference?

Three common ways keep a service one tap away on an iPhone, and they behave differently in ways that matter day to day.

If you only want quick access, a bookmark is enough. If you want the site to feel like an app and keep a login of its own, install it. If you need something only a native app can do, you need the App Store version, if the service has one. The middle column hides most of the surprises, and Home-screen web app vs Safari tab: cookies, logins and storage goes through them one by one.

Why does this matter for privacy?

The detail most people miss is that an installed web app and Safari are two separate places as far as the website's data is concerned. WebKit's notes on Safari 17.2 explain what happens: when you add a site to the home screen, its cookies, including any login state kept in them, are copied into the new web app once, and after that no other website data is shared between the two. A login or logout in one does not carry over to the other, and whatever the site saves on your phone, from drafts to downloaded files, sits in that app's own store rather than in Safari's; Home-screen web app vs Safari tab works through the consequences.

What separation is not is a lock. Anyone who can unlock your phone and tap the icon gets whatever the site shows, and if the site keeps you signed in, they are signed in too. Nothing about being a PWA changes that. Can you password-protect a website on your iPhone? walks through the options, from Apple's built-in controls to a separate password in front of the app.

One more consequence: separate storage is still browser storage. It is not backed up anywhere unless the site itself does that, and WebKit's storage policy allows it to be evicted. Treat anything a web app keeps only on your phone as convenient rather than safe.

Where does PWA Lock fit in?

We make PWA Lock, so read this section as the makers' view. PWA Lock gives a web app a locked copy at its own address, and that locked address is itself a small PWA: its manifest names the installed icon after your app and uses the cover's icon, and its service worker saves the cover so that the Calculator, 2048 or whichever cover you chose opens and works even when you are offline. Unlocking always needs a connection, because the password check and the pages behind the lock are fetched live rather than saved for offline use. Set up PWA Lock on your iPhone: the complete guide has the steps.