It might be that everyone is comfortable with knowing all of this – but it’s worth a reminder to check.
Facebook privacy example We were quite naïve in the early days of social media so we would encourage you to perform a privacy check up to see what others can see that you have posted or been tagged in. You can also choose what is visible in your timeline. Turn on “Review posts that friends tag you in” (go to “Privacy shortcut”/“See More Settings”/“Timeline and tagging”) so you can approve posts where your friends have tagged you before they appear on your timeline. If you tag a friend or two in a photo, all of their friends will be able to see the posts as well. The same goes when you post something on someone else's profile page: The audience is set by that person, not by you. This doesn't mean you need to forgo sharing entirely—just bear in mind that tagged images can be seen by people outside your intended audience
Instagram has a very simple privacy setting: either you share posts with anyone (account configured as “Public”) or only people you have previously approved to follow you can see your content (account configured as “Private”).
We strongly encourage you to set is as “Private” by going to “Options” and enabling the “Private Account” function. Once this is done, it is important that you do not accept requests from people that you do not know in the offline world.
Twitter To make your Twitter profile private, click on your profile picture and click Settings and privacy. Then go to the Privacy and Safety tab and make sure that Protect My Tweets is checked.