This article provides step-by-step instructions for three ways to mark text messages as unread on an iPhone running iOS 16 or later. With this information, you can mark messages to come back to later when you have time to read and respond to them.
How to Read Unread iMessages on iPhones!
Starting with iOS 16 (and iPadOS 16 on the iPad), you can mark text messages as unread in the preinstalled Messages app (you can also pin conversations to the top of the window and mute notifications from them). If you're running an earlier version of iOS on your iPhone, you won't have this feature, and it's one of the many good reasons to upgrade.
Go to the Messages view, which shows all of your conversations. When you're in a conversation, tap the arrow in the top left corner.
From this screen, there are three ways to mark a text as unread. For the first, tap Edit > Select Messages > tap each conversation you want to mark as unread > Unread.