Why iPhone apps can't watch your clipboard either

Last week we wrote about why Android clipboard apps can't watch your clipboard. The iPhone is strict in a different way. Android leaves one door open, the keyboard, and lets it listen even when it is hidden. iOS leaves nothing open in the background at all.

This post covers the rules, what is left for a clipboard app once you follow them, and the parts of Clypy on iPhone that still ask more of you than Clypy on a Mac.

The rules

Three rules shape everything a clipboard app can do on iOS.

Only the app on screen can read the clipboard. There is no background service and no notification when something new is copied. An app that is not in front sees nothing.

Reading another app's copy is visible. Since iOS 14, the system shows a banner when an app reads something copied in a different app without you asking it to paste. Since iOS 16 it goes further: an app that reads the clipboard on its own, rather than through a system paste button, gets an Allow Paste prompt. iOS 16.1 added a setting for each app, Paste from Other Apps, with the choices Ask, Deny and Allow.

Extensions are not told either. A keyboard or a widget runs in its own process, and iOS does not tell it when the app you are typing into copies something.

We think the first two rules are right, for the same reason Android's is. Your clipboard sees passwords, one-time codes and addresses, and the iOS 14 banner caught plenty of apps reading it every time they opened. The cost is that a clipboard history on iPhone can never be fully automatic.

What that leaves a clipboard app

Follow those rules and four moments remain when a clipboard app may legitimately read what you copied:

1. Opening the app. Clypy reads the clipboard whenever you bring it to the front, and saves what is new.
2. The Clypy keyboard, while it is on screen. Switch to it with the globe key and it saves your latest copy, then keeps saving new ones for as long as it stays up.
3. The share sheet. Share text, a link, a picture or a file to Clypy from any app.
4. Shortcuts. Clypy's Copy to Clypy action saves whatever a shortcut hands it, without opening the app.

The fourth is how Back Tap works. Back Tap only lists shortcuts you made yourself, so the setup is a two-step personal shortcut, Get Clipboard followed by Copy to Clypy, chosen in Settings, Accessibility, Touch, Back Tap. After that, a double tap on the back of the phone saves your clipboard. The Action button on recent iPhones can run the same shortcut.

Asking without asking

The Allow Paste prompt is what makes or breaks a clipboard app on iPhone. If opening the app asks for permission every time, people start tapping Don't Allow, and then nothing gets saved.

So Clypy checks before it reads. Apple lets an app ask a few questions about the clipboard without triggering the prompt: whether it has changed since last time, through a counter called changeCount, and whether it holds text, a link or an image. Clypy asks those first and reads the contents only when there is a copy it has not seen. Open the app five times in a row and it reads the clipboard once.

It also remembers your answers. Tap Don't Allow and Clypy will not ask again about that same copy. And anything the copying app marks as concealed or temporary, which is how password managers label passwords, is skipped without being read at all.

The simplest fix is still yours to make. In Settings, Apps, Clypy, set Paste from Other Apps to Allow, and iOS stops asking. Clypy's own Settings, Capture shows which one you have chosen.

The keyboard, and why it polls

Android tells the selected keyboard about every copy, even while the keyboard is hidden. iOS does not. While the Clypy keyboard is on screen it may read the clipboard, but iOS will not tell it that the app you are typing into has just copied something. Apple's notification for clipboard changes does not cross from one process to another.

So the keyboard checks. Once a second, while it is on screen, it reads the change counter, which costs nothing and reveals nothing. When the number moves, it reads the new copy and saves it. When you switch away, the timer stops: iOS gives a keyboard no time in the background, and a timer for a keyboard nobody can see would only use battery.

When the keyboard saves a copy, it does what the Android keyboard does. It encrypts the clip, writes it to the library it shares with the app, and sends that one change to your other devices through our relay as a background upload. Your Mac can have it a moment later without the Clypy app ever opening. The relay stores nothing, so this only reaches devices that are online at the time; the rest catch up when they next sync.

Reading the clipboard from a keyboard needs Full Access, which iOS asks you to grant in Settings. Clypy uses it to read the clipboard and your synced history, and never logs what you type.

Two honest limits follow from all of this:

• The keyboard saves copies only while it is on screen. Copy three things while typing with Apple's keyboard, then switch to Clypy, and it saves the one on the clipboard now. The two before it are gone. Unlike Android's Save while hidden, there is no setting that changes this on iPhone.
• It pastes text, not pictures. Pictures you have saved show up in the keyboard, but a keyboard can only insert text. To use a picture, open the app and copy it from there.

The direction that is harder: clips coming to the phone

Copying on your computer and pasting on the phone is the harder direction, and the answer is the same as on Android. While Clypy is open, clips arrive straight away. While it is not, iOS runs a background refresh when it chooses to. Clypy asks for one at least every 15 minutes, but iOS treats that as a minimum and decides for itself based on how you use the phone. A phone that never opens Clypy may never run one.

Nothing wakes the phone the moment you copy on your Mac. That would take Apple's push notification service and a server that keeps a token for each of your devices, and our relay keeps nothing in storage. The keyboard does not sync on its own either: it shows what the app has already received. If a clip from your computer is not there yet, open Clypy for a second and it will be.

What this means if you use Clypy on iPhone

• Set Paste from Other Apps to Allow for Clypy, so opening the app never asks.
• Switch to the Clypy keyboard just before you paste. It saves your latest copy as it opens, and anything you copy while it is up.
• Set up Back Tap with Get Clipboard, then Copy to Clypy, for copies you want to keep while you work in other apps.
• Share pictures and files to Clypy instead of copying them.
• If a clip from your computer has not arrived, open the app.
• If your computer is a Mac, Universal Clipboard still works, and Clypy on the Mac saves whatever it brings over. Our guide to copying between an iPhone and a Mac covers both.

Opening the app and the share sheet are free, with unlimited local history. Sync, the keyboard, widgets and Shortcuts are part of Clypy Pro.

iOS asks more of you than a Mac does, and that is the price of a clipboard that apps cannot read behind your back. Hopefully Apple opens it up someday, perhaps with a permission you could give one clipboard app you trust, the way Android lets the keyboard you choose hear every copy. Until then, we would rather build around the rule than around a gap in it that Apple would close. If you are just looking for what the iPhone keeps on its own, start with how to see clipboard history on an iPhone.