When you purchase an app, you can install it on all of your iOS devices. Even if you use a different Apple ID for each device, you can log in to each account and download the apps directly to a single iPhone. When it comes time to update an app that uses a different Apple ID, a prompt displays asking you to confirm the password for the account. While Apple allows you to download apps to multiple devices, you can't download DRM-protected music, videos and other content purchased from the iTunes store using more than one Apple ID.

Single Apple ID

Step 1

Tap the "Settings" app.

Step 2

Select the "iTunes & App Stores" option.

Step 3

Set the "Apps" toggle switch to the "On" position in the Automatic Downloads section. Complete this process for each of your iPhones.

Multiple Apple IDs

Step 1

Choose the "Settings" app.

Step 2

Select "iTunes & App Stores."

Step 3

Tap your Apple ID and press "Sign Out."

Step 4

Input your credentials for your other iPhone in the "Apple ID" and "Password" fields. Select the "Sign In" button.

Step 5

Double-click the "Home" button. Check to make sure the App Store icon doesn't display in the Multitasking bar by swiping from left to right to view all currently open apps. If you find the App Store, hold the icon until the icons begin to wiggle, and tap the "-" symbol to close the app.

Step 6

Click the "Home" button twice to return to the Home screen.

Step 7

Tap the "App Store" app.

Step 8

Select the "Updates" tab and choose "Purchased."

Step 9

Tap the cloud icon next to each app you want to install. You can select the "Not On This iPhone" tab to show only apps that you haven't yet installed. Complete the process for each Apple ID you purchased content with on both of your iPhones. This process allows you to keep the apps installed from multiple Apple IDs on your iPhone.