Whatever your reasons for wanting to cancel a friend request, if the other person hasn't accepted or denied the request, you can still cancel it. How you go about canceling a friend request varies slightly depending on whether you're using Facebook in your Web browser or in the official Facebook app on your mobile device.
Canceling a Pending Request in Your Web Browser
To cancel a pending friend request in a Web browser, click the "Friend Request" icon located at the top of any Facebook page. Select "Find Friends" and then click "View Sent Requests" to display a list of recent friend requests. Hover your mouse over the "Friend Request Sent" link located beside the pending request you want to cancel and select "Cancel Request."
Canceling a Pending Request in the Facebook App on Mobile Devices
To cancel a pending friend request in the official Facebook app on an Android or iOS device, start by tapping the "More" icon. The More icon is identified by three horizontal lines. Tap the "Find Friends" link in the Apps section and then tap "Requests." Tap the down-facing arrow located next to Friend Requests and select "View Sent Requests." Tap "Undo" next to the pending request you want to cancel.