Posting an update to Instagram doesn't have to mean sharing your life with every single person you've befriended there. In fact, all of the major social apps give you more granular control than you might realize.

If you want to set up a private, select group of people to show off photos of your baby to—or to keep your most raucous nights out a secret from—you can do so without resorting to emails or group chats.

We'll show you how to lock down your Facebook, Instagram, Twitter, and Snapchat accounts below, but a word of warning: There's nothing to stop someone in your private circles taking a screenshot of what you've shared and making it public. So even with your settings dialed in, be careful what you share, and with whom.

Facebook

Facebook has a long history of privacy failures, but at least it provides ample tools for restricting the audience of your posts. Start to write an update on the web, and you'll notice drop-down menus next to both News Feed and Your Story, the two places where your post can appear.

These menus probably say Friends by default, but if you open them up, you can be more selective about who will see your post. You can even make it public, if you want, visible by anyone on the web, even if they're not one of your confirmed friends on Facebook.

Courtesy of David Nield

Click More then See All on the drop-down menu, and Facebook lets you set up a list of specific friends who can see the post—just your relatives, for example, or the people who work in your office. You can also opt for Friends except, which includes all of your Facebook friends apart from whomever you exclude, or Specific friends, which limits distribution to a smaller list of your choosing.

It's important to remember that the audience you select because the default for any subsequent posts, until you change it back again. Unless you change the audience for your posts back to Friends, for instance, any posts you publish on Facebook will only be visible to the custom list of people you've just created.

These same options are available in the Facebook apps for Android and iOS, and just about anywhere you can post to Facebook from. Again, you'll see a drop-down menu—most probably set to Friends, as that's the default—and again you can tap on it to change the audience for a post. Not everyone in your Facebook network needs to see your next speed-eating challenge, you know?

Twitter

Tweeting is much more straightforward than posting on Facebook. There's no granularity to it; your account is either public, meaning anyone on the web can see your posts, or private, which limits the audience to followers you've specifically approved.