You want to take pictures on your phone without being seen. The camera's shutter sound can give you a clue. There's no setting you can change to silence it, which is a major design oversight.

There are two ways to turn off the shutter noise of your phone. You can be a photo snapping ninja if that's what you do.

How to turn off the camera sound on an iPhone with the ring/silent switch

To silence the camera's shutter sound, put your phone in silent mode.

The Ring/Silent switch is located on the left side of your phone and can be flipped down to reveal the orange color behind it.

The side of an iPhone, with the Ring/Silent switch flipped to Silent mode. The orange color behind the switch is showing.
Flip the Ring/Silent switch to Silent mode.
Stefan Ionescu

You have to flip the Ring/Silent switch away from you on older phones.

The trade-off is that you won't be able to hear calls or notifications because the phone's ringer will be silenced.

How to turn off the camera sound on an iPhone with Live Photos

You can take a Live Photo if you don't want to put your phone in Silent mode, but still want to record a short video.

There is a way to take a Live Photo on an Apple device.

You can't take Live Photos on newer phones.

This is the first thing. On your phone, open the camera app.

There are two The screens have circles at the top of them. Live Photos is on if they are yellow. It's off if they're white with a slash running through them.

A combined picture of the Camera app on iPhone. The left picture shows the concentric circles at the top are yellow, and they have been highlighted. The right picture shows the concentric circles are white, and they have been highlighted.
When the concentric circles at the top are yellow, Live Photo mode has been enabled.
Stefan Ionescu

There are three. The camera won't make the shutter sound if you tap the shutter button.

The Camera app on iPhone, with an arrow pointing to the “Shutter” button.
Tap the "Shutter" button.
Stefan Ionescu

If you don't have enough space on your phone, you may not be able to use this method for a while.