How can I check who can see what I post?

A lot of oversharing is not really oversharing - it is the default settings quietly showing your posts to more people than you meant. Most platforms start out public, or close to it. A few minutes in the privacy settings puts you back in control of who sees what.

What "public" really means

A public post can be seen, saved, screenshotted, and reshared by anyone - not just your followers - and can turn up in search.
Your profile often gives away more than your posts: photo, bio, friends list, and who you follow.

The settings worth checking

Account visibility. Consider a private account for your personal life, so you approve who follows you.
Per-post audience. Many apps let you choose who sees each post - public, friends, close friends. Check what the default is set to.
Profile details. Hide your friends list, contact details, birthday, and location where you can.
Interactions. Set who can message, comment, tag, and mention you.
Discoverability. Turn off "find me by phone number or email" if you would rather not be looked up.
Past posts. Most platforms have a "limit past posts" option that tightens old content in one go.

A quick habit

Every few months, look at your own profile while logged out - or as the public sees it - to check what a stranger can actually find. Settings drift, and platforms sometimes reset them.

If you only do one thing

Open your main platform's privacy settings and set your default post audience on purpose, rather than leaving it on whatever it came as.