Record suspicious activity
In some cases, such as if you see a notification that someone is attempting to use your Apple ID to sign in on a new device, you may want to take a screenshot or record video of the screen. You can then save these as image or video files on your iPhone, iPad or Mac.
Find out how: To view a task below, select the plus button 
next to its title.
Take a screenshot or screen recording on your iPhone or iPad
Do one of the following:
On your iPhone or iPad with Face ID: Simultaneously press and then release the side button and volume up button.
On your iPhone or iPad with a Home button: Simultaneously press and then release the Home button and the side button or Sleep/Wake button (depending on your model).
Tap the screenshot in the lower-left corner, then tap Done.
Choose Save to Photos, Save to Files or Delete Screenshot.
If you choose Save to Photos, you can view it in the Screenshots album in the Photos app, or in the All Photos album if iCloud Photos is turned on in Settings > Photos.
Take pictures or screen recordings on your Mac
Press Shift-Command-5 (or use Launchpad) to open the Screenshot app and display the tools.
Click a tool to use to select what you want to capture or record.
For a portion of the screen, drag the frame to reposition it or drag its edges to adjust the size of the area you want to capture or record.
Action
Tool
Capture the entire screen
Capture a window
Capture a portion of the screen
Record the entire screen
Record a portion of the screen
Select any options you want.
The available options vary based on whether you’re taking a screenshot or a screen recording. For example, you can choose to set a timed delay or show the mouse pointer or clicks, and specify where to save the file.
The Show Floating Thumbnail option helps you work more easily with a completed shot or recording. It floats in the bottom-right corner of the screen for a few seconds so you have time to drag it into a document, mark it up or share it before it’s saved to the location you specified.
Start the screenshot or screen recording:
For the entire screen or a portion of it: Click Capture.
For a window: Move the pointer to the window, then click the window.
For recordings: Click Record. To stop recording, click the Stop Recording button
in the menu bar.
When the Show Floating Thumbnail option is set, you can do any of the following while the thumbnail is briefly displayed in the bottom-right corner of the screen:
Swipe right to immediately save the file and make it disappear.
Drag the thumbnail into a document, an email, a note or a Finder window.
Click the thumbnail to open a window; there you can mark up the screenshot — or trim the recording — and share your result.
Depending on where you chose to save the screenshot or recording, an app may open.