Secondary Tumblr blogs are becoming more popular, as people want to keep their blogs separate from their personal lives. However, secondary Tumblr blogs are not always private. In fact, sometimes people can see your secondary Tumblr blog if they know the URL.
Additionally, if you use a public blog address for your secondary Tumblr blog, anyone can see it. Therefore, it is important to be careful about what information you share on your secondary Tumblr blog and to make sure that the URL is not publicly available.