If you want to pin a WhatsApp chat on an Android device, long-press the chat until a green tick appears next to the avatar. At the top of the screen, you will now see a pin icon. Tap it.
The chat will now have a pin and remain at the top of the screen, regardless of your future chat history with other contacts.
The iPhone method is slightly different but no less difficult. Swipe right on the chat you wish to pin and tap Pin.
The pin icon will now appear next to the chat and will remain there until the chat is unpinned. The chat will jump to the top of the screen and will remain there regardless of your future chat history with other contacts.
WhatsApp Web is similar to WhatsApp desktop when it comes to pinning chats. To pin a chat in WhatsApp Web, click the chat to highlight it. Then click the downward arrow on the right and select Pin chat.
If you use the desktop version of WhatsApp, you can pin a chat in one of two ways. The first method is to click on the chat to highlight it. Then click the downward arrow to the right of the chat and select Pin chat from the menu.
The second option is to click the chat to highlight it. Then go to Chat > Pin Chat at the top of the screen.