Udacity has around 200 courses that are completely free (but do not offer a certificate). Usually these courses were created as part of a paid microcredential that Udacity offers called a Nanodegree.
In previous years, Udacity released a large part of courses in a Nanodegree for free, but recently, Udacity has drastically reduced the number of free courses they launch. Many of the courses that are part of newer Nanodegrees are not free.
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