edX

EdX is the ideal combination of high-quality courses and ease of use, that is one of the Online Courses to Learn Grammar. There are various lessons focusing on improving grammatical skills, as well as full-fledged programs, on the site (small groups of courses with a common goal, like a miniature version of a college major). EdX's grammar courses are mostly part of its language offerings. The bulk are geared at English language learners (or those wishing to brush up on certain skills such as essay writing or writing/speaking in business situations), although there are others that focus on grammar in other languages.

If you're contemplating EdX, good news: most of their courses are free—at least to take. You're good to go if you're taking a grammar course to brush up on your abilities on your own, but the "certified certificate" of completion costs anywhere from $50 to $300 per course if you're doing it for more official purposes. Classes, like Coursera, begin with an enrollment cycle, but once the session begins, students can choose between instructor-paced courses, which have a predetermined timetable, and self-paced courses, which allow students to pace themselves and go at their own speed.