Trailforks has a variety of settings to control various levels of privacy for user's activities or ridelogs.
On iOS and Android:
You can control the visibility of each activity or ridelog when you are saving the activity/ridelog:
On Web:
When adding or editing an individual ridelog, there are some settings at the bottom of the form.
Unselecting "Public" means that only you will be able to view this ridelog; the ridelog won't show on friends dashboards, the activity feed, or any ridelog lists. If a user tries to view your ridelog, they will get an error page. When you view it, you'll see the below message informing you the ridelog is private.
The 2nd option "Hide GPS & Trails Ridden" means your ridelog is still public as far as basic details, like title, friends, distance, and time. But any location details are hidden, such as the exactly location, map, & trails ridden. This is useful if your ride contained some secret or sensitive trails. 
When bulk importing rides from Garmin, you can apply privacy settings on all the imported items.
For rides imported from Strava, the GPS data within your "privacy zone" is not imported. If you granted Trailforks permission to read your private Strava activities, they will remain private ridelogs when imported. Any imported Strava activities will also remain private in Trailforks. For more information on the integration between Strava and Trailforks, please see this article.
If we detect your ridelog goes along any "hidden/secret" trails your ridelog will be flagged as "sensitive". The hidden trails won't be show in the list of trails ridden and this message will be displayed.
Trailforks has several heatmaps which can be used to fill in missing trails or to get a visual sense of the most ridden trails in an area. Your ridelog won't be used in the heatmap data if it's not public; the hide GPS option is checked or it's flagged as "sensitive".
Also related is your profile page's privacy. By default, your profile page is public, so people not logged into the site can view your profile and your public ridelogs (these are not indexed by search engines, however). There is an option in your profile settings page to make your profile, and all its sub-pages, not public.
SETTING UP PRIVACY ZONES
Trailforks by default asks for the "view_private" permission as many users want to import their private rides to Trailforks.
When a private Strava ride is imported it remains private on Trailforks. However, any Strava privacy zone cropping is ignored.
You have 2 options:
A. You can choose to uncheck the "view_private" permission and not import any private activities.
B. You can setup privacy zones on Trailforks and have them cropped like Strava does. Look for the privacy zone feature in your profile settings.
If this is something you're interested in doing, you will have to go to your Trailforks settings and disconnect Strava, then re-connect here: https://www.trailforks.com/ridelog/stravaautoimport/.
Privacy zone setup on Trailforks:
