Messages carries two different location switches on two different systems. On iPhone, Messages shares through Find My, and Apple says the person that you stop sharing with won't be notified, while Apple's Personal Safety guide adds that they may notice you've stopped. On Android, Google Messages shares through Google Location Sharing, so stopping the share there stops it for every Google app that uses it.
Do they get told?Apple says the person that you stop sharing with won't be notified, while Apple's Personal Safety guide adds that the people you previously shared with may notice that you've stopped and that on earlier operating systems they may receive a notification in Messages. Apple's iPhone guide says the previous bubble in the conversation no longer displays a map. Google's Messages page does not document whether the other person is told when you stop, though Google does document a notification to the recipient when a share starts.
Do they get told?Whether the other person is told when you stop is not documented on Google's Messages page, which does not describe what they see afterwards. What is documented is the other direction: Google says that when you start a share the recipient gets a notification, or an email if they have neither Find Hub nor Google Maps.
Who can still see you
Off
That one person or group
Google says stopping a share stops it for your account and for every app using Google Location Sharing, not just this chat.
Still on
Your other shares and every app
Shares you started with other people carry on, and the Messages app keeps its own location permission.
Still visible
The network
Your carrier and any site you open still place you roughly by cell tower and IP address.
Google prints the sharing lengths as For 1 hour, Today only, Until you turn this off, and a Custom duration that cannot last more than 24 hours.
Do they get told?Google documents what this does rather than who is told: your shares stay in place, but they stop being updated with your real-time location until you turn the setting on again. Google's page describes no notice to the people you share with.
Who can still see you
Off
Live updates to all your shares
Everyone you share with stops getting new positions from this device until you turn the setting on again.
Still on
The shares themselves
Google says this does not stop any of your shares, and other location services such as Maps keep working on the device.
Still visible
The network
Your carrier and any site you open still place you roughly by cell tower and IP address.
Google says this setting is device and account specific, so you set it on each device you are signed in on.
Do they get told?What the people you share with see when Messages is set to Don't allow is not documented on Google's app-permissions page. What is documented is the effect on the app: Google says it cannot use the permission, even when you're using the app.
Who can still see you
Off
The Messages app on this phone
Google says the app cannot use the permission, even when you are using the app, so Messages has no position to send.
Still on
Google Location Sharing and other apps
The account-level sharing setting and every other app on the phone keep their own permissions.
Still visible
The network
Your carrier and any site you open still place you roughly by cell tower and IP address.
Google's page describes the per-app steps generically; Messages is the app you select at the third step.
Location spoofing, fake-GPS apps and mock-location settings are outside this site on purpose. This page describes the settings the app and your phone provide, and what the vendor documents about them.
If someone is tracking you against your will, turning a setting off may not be the safest first step. Read this first.
Every platform this site carries for Messages is on the
Messages guide.