Use a peek to provide a live, content-rich preview of an item. It’s best when a peek gives users enough information about an item to augment their current task. For example, users can use peek to preview the webpage of a URL in a message before they decide to open the webpage in Safari or share the link with their friends. In a table view, peek shows users the detail view for a row item.
Provide a pop for every peek. Even though a peek should give users most of the information they need, you should always let users transition to the pop if they decide to switch away from their current task and focus on the item. The pop should be the same view that users get when they tap the item.
Don’t enable both peek and the Edit menu for the same item. It can be confusing when both features are enabled for one item. (To learn more about the Edit menu, see Edit Menu.)
Within a peek, avoid displaying elements that look like buttons. If users lift their finger to tap an element that looks like a button, the peek disappears.
Provide peek quick actions, if appropriate. Within a peek, users can swipe up to reveal actions that are related to the item. For example, peek quick actions in Mail include Reply All, Forward, and Move Message. Not every peek needs quick actions, but if you already provide custom touch-and-hold actions for an item, it’s good practice to provide the same actions within the peek that replaces touch and hold for that item. (Note that peek quick actions in a peek for a web view are supplied automatically.)
Don’t use peek as the only way to enable item-specific actions. Not every device supports peek and pop and some users may choose to turn off 3D Touch, so it’s essential to find other ways to make peek functionality available in your app. When your app runs on older devices, it can make sense to mirror a peek’s quick actions in a view that users get when they touch and hold an item.