Does J.K. Rowling have a blog? There is no definitive answer, but it seems likely that she does. Rowling has spoken openly about her love for writing, and has even discussed her blog on occasion.
Additionally, many of the references to writing that appear throughout her novels could easily be construed as blog posts. Given her affinity for blogging, it would not be surprising if Rowling had a personal blog where she discusses her work and thoughts on writing.