When I write something, there maybe one or few grammar mistakes. Is there any online service like thing (for free) that can correct those for me? Just a curiosity to know.
I am partial to Grammarly. In my experience, it is the best, and you can start with a free account.
I also have to point out that none of the grammar-checking software packages are perfect. They can help you, but they will not do your job for you, you still have to decide in every word-by-word and sentence-by-sentence case whether to follow their advice of not.