How To Make All Public Posts Private On Facebook

To make all your public posts private on Facebook, you can follow these steps:

Log in to your Facebook account using your credentials.
Click on the downward-facing arrow in the top-right corner of the Facebook interface.
From the drop-down menu, select "Settings & Privacy" and then choose "Settings."
Privacy Settings:

In the left-hand menu, click on "Privacy."
Under the "Your Activity" section, click on "Limit Past Posts."
A popup window will appear, explaining the consequences of changing your past posts' privacy settings. Read through the information, and if you're comfortable proceeding, click on the "Limit Past Posts" button.
This action will change the privacy setting of all your past public posts to "Friends" only.
Future Posts:

To ensure all your future posts are private, return to the "Privacy" section.
In the "Your Activity" section, click on "Edit" next to "Who can see your future posts?"
Choose "Friends" from the drop-down menu. This setting ensures that any new posts you make will only be visible to your friends.
Reviewing Privacy:

To review how your posts will appear to the public or specific individuals, click on "Tools" in the left-hand menu of the "Privacy" section.
Select "Privacy Checkup."
The Privacy Checkup will guide you through various settings, such as who can see your profile information and who can contact you. Make sure to review and adjust these settings according to your preferences.
Remember that these steps will only affect your own posts on Facebook. If you've been tagged in someone else's public posts, you will need to adjust the privacy settings for those posts individually or contact the person who made the posts to ask them to adjust the privacy settings.