It is “Ginger”.
It is a simple application to correct English spelling and grammar developed by an Israeli company. It is able to not only check the spellings but also offer an appropriate expression fitting the context. For a Japanese it is difficult to choose a right preposition. Ginger helps me to learn the precise usage of prepositions. The function of Ginger is much stronger than MS word, Google translation, or other spell checkers.
I installed Ginger into my Chrome, to correct the errors in my past entries. To be ashamed of, innumerable errors were detected.
Correction is automatically performed. I do not know why, but Ginger has a bug to misunderstand Capital letters. Besides this, I am fully satisfied with it.
Ginger also equips learning English mode. It costs you $4.9 per month. I wonder if I should try it.