Yes and no. There are definitely some courses on Coursera that are paid only. These are indicated by a small green $ symbol.
A big majority of the courses have some element of “free” — mostly the videos are free to watch but you need to pay if you want access to graded assignments and certificates. If you search for free courses on Coursera’s website, you will see a sticky note at the top of the search results explaining that lectures and non-graded material are free. However, Coursera still has many courses for which the graded assignments are free. An investigation by Class Central discovered 1700 Coursera courses that are still completely free, without a certificate.