You can disable Smart Matches for a particular tree by changing your Privacy Settings:
1. Log into your family site.
2. Click on your name in the upper right-hand side of the screen.
3. Select ‘My Privacy’.
4. Under the ‘Content’ section you can select how your family tree and photos can be searched by other MyHeritage members.
Here you can find two options: 'Enable Smart Matching™ on MyHeritage (recommended)' and 'Enable Smart Matching™ with other MyHeritage websites and partners'. You can uncheck any of them (or both) according to your preferences.
Note: you can click on the sign to read more information about Smart Matching™ and the benefits you get when these options are turned on.
Note: Disabling Smart Matches for your family site doesn't disable the Smart Matches you get in Family Tree Builder. To disable the feature in your Family Tree Builder, please read: How can I disable Smart Matching for Family Tree Builder?