First, both you and the person who receives your text must have updated to iOS 17 on your iPhone (or iPadOS 17 on your iPad). You can also use the feature on a Mac for which you must be running MacOS Sonoma or later.

Also: Upgrading to MacOS Sonoma? Do these 7 things first

To check your mobile device, go to Settings, select General, and then tap Software Updates. You’ll be told that your device is up to date or prompted to download and install the latest update. To check your Mac, click the Apple icon and select System Settings. Select General, click Software Update, and then click the button to upgrade to MacOS Sonoma.

Next, you’ll need to enable location sharing on your device. For this, head to Settings, select Privacy & Security, and then tap Location Services. Swipe to the bottom of the screen, choose System Services, and turn on the switch for Share My Location.

You’ll now want to determine which data you want to share with another person. Go to Settings and select Messages. Swipe down to the Check In section and tap Data. You’re given two choices. Selecting Limited shares your most recent location and details about your battery and network signal. 

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Selecting Full shares all the data included in the Limited option but adds the route you took and the location of your iPhone the last time it was unlocked. Choose your preferred option.

Now that you’ve set up the Check In option, it’s time to try it. Open the Messages app and select a trusted person with whom you want to share your location. Only contacts with whom you have a history will be eligible. Tap the + icon in the lower left to display the iMessage apps. Swipe down the screen to see all the apps. If the person qualifies, you’ll see an app for Check In in the list. If so, tap Check In. The text message is then generated on your end. Tap the Edit button in the text to tweak the different settings.

You now have two choices for setting your expected arrival time — When I arrive and After a timer. To set the time for when you physically arrive at the location, tap the heading for When I arrive. Under the displayed map, tap the Change button. In the Search field, start typing the address for your destination and then tap it from the list. The location appears in a larger map on the screen. You can narrow or widen the area included in your destination by tapping Small, Medium, or Large at the bottom. When finished, tap Done.

Next, choose the type of transportation you’ll be using — Driving, Transit, or Walking. If you plan to make any stops or otherwise pause along the way, tap the Add Time link and select 15 minutes, 30 minutes, or 1 hour to add to the timer. Tap Done.

If instead, you want to set a specific timer for your arrival, tap the heading for After a timer. 

Also: How to use iOS 17’s ‘Live Voicemail’ transcriptions

At the timer screen, swipe up or down to change the number of hours and minutes for your arrival time. When finished, tap Done.

Back at the Messages screen, tap the blue arrow to send the text to the recipient.

The person on the receiving end gets a notification of your Check In explaining how the process works. They then tap OK and choose to allow Check In to send critical alerts if they wish. Such alerts can get through even if the phone is muted or in Do Not Disturb mode. The Check In text appears in the recipient’s Messages app. Tapping the Details button displays the ETA and a notification that the person will be notified when you arrive.

If you chose the option for After a timer to set your check in to a specific interval, you can add a specific number of minutes to increase the time. Open the message and tap its Details button. At the next screen, tap the Add Time link and then select 15 minutes, 30 minutes, or 1 hour to extend your arrival time. Tap Done.

To cancel the Check In, open the message and tap its Details button. At the next screen, tap the Cancel Check In button. Confirm your action by tapping Cancel Check In.

Otherwise, allow the timer to proceed. When your timer has ended, you can tap the End button.

Also: How to better organize text messages on your iPhone, thanks to iOS 17

If not, the recipient will receive a notification that the Check In has ended.

If you fail to end the timer, or a certain number of minutes pass after the countdown has elapsed, the recipient will receive a critical notification. Tapping the notification will take them to the original text message. From there, tapping the Details button displays a screen where the recipient can call you or check your location on a map.