Step 1: Go to the Clock app and select the Timer tab.
Step 2: Tap on “When Timer Ends.” This is where you would normally select what ringtone you want the timer to use when the time is up.
Step 3: Scroll all the way to the bottom and select “Stop Playing” and tap “Set” in the upper right corner to confirm.
Step 4: Set the timer to whatever time you want, and hit the “Start” button.
If you’re playing music or a movie on your iPhone, the music or the movie will now stop playing when the time is up.
Be careful though! If in the future you need to set a timer with a ringtone, remember to go back in the Timer settings and change the “Stop Playing” action to an actual ringtone.