To access your timeline's visibility settings, click the visibility status above your timeline (it will say Public, Private, etc).
Anyone on the internet can see your timeline. Your timeline will also be visible in search engines like Google and Bing.
Only you can see the timeline while signed in to your account.
If you're using Preceden's collaboration feature, anyone you invite to be able to edit your timeline will also be able to see it.
Similar to private, but your timeline's web address will also be updated to include a unique difficult-to-guess code. For example, here's a real timeline that is accessible using a Secret URL:
That 43dbc32502bb305d is a randomly generated code that Preceden associates with your timeline. If anyone tries to access the timeline without that exact code, Preceden won't let them.
If your timeline is already accessible via a Secret URL but you want to change the code so anyone who you previously gave the link to no longer has access, update the visibility to Private then change it back to Secret URL. This will cause Preceden to regenerate the code.
Also similar to private, but you'll also be able to set a password which you can give to others along with your timeline's URL so they can view it.
When you sign up for an account, if you select that you're using Preceden for School then your timelines will be public by default. These student timelines are generally historical timelines that can benefit other students by being public which is why that's the default. The visibility can easily be updated to one of the other options using the timeline settings.
Also, if you're a student using Preceden through your teacher's account, your timelines are private and cannot be made public. The only other person who can see your timeline is your teacher.
For all other account types, your timelines are private by default.
Sharing a Link to Your Timeline
See Share a Link to Your Timeline for more details.