To turn off a Samsung Galaxy S21, you have a few easy options. Here are the main ones you’ll actually use in daily life.

1. Fast way with buttons

  1. Press and hold Power (Side key) and Volume Down together for about 2–3 seconds.
  1. When the menu appears, tap Power off.
  1. Confirm by tapping Power off again if asked.

This works even if Samsung has remapped the side key to Bixby on your phone.

2. Using the Quick Settings panel

  1. Swipe down from the top of the screen.
  1. Swipe down a second time so Quick Settings fills the whole screen.
  1. Tap the power icon at the top (often in the top-right).
  1. Tap Power off , then confirm.

This method is handy if your buttons feel awkward or you’re already in the notification shade.

3. With Bixby (voice method)

If Bixby is enabled:

  1. Press and hold the Side key to launch Bixby.
  1. Say: “Turn off my phone” or “Restart my phone.”
  1. Confirm on-screen if prompted.

This is useful if your buttons are damaged or hard to press.

4. If holding the side key opens Bixby, not power menu

On many S21s, a long-press of the side key opens Bixby by default instead of the power menu.

You have two choices:

  • Still use Power + Volume Down to get the power menu.
  • Or go into settings and change the side key behavior so a long-press shows the power menu instead of Bixby. (This option is mentioned by users discussing how the key defaults can be changed in settings.)

Quick recap (in plain language)

  • Easiest universal method: Hold Power + Volume Down → tap Power off → confirm.
  • No buttons: Swipe down twice → tap power icon → Power off.
  • Hands-free: Hold side key → tell Bixby “turn off my phone.”

Information gathered from public forums or data available on the internet and portrayed here.