By that I mean, an online presence that no one (or very few people) in real life know about? A secret blog perhaps?

I do YouTube videos. My most popular video has over 70,000 views. Only my DH knows about it, partly because I would feel weird about people I know watching me on YT, and partly because some of the things I talk about are controversial. Sometimes I wonder what they would think if they stumbled upon them accidentally and realized it was me.