Journal article: During the 2019 European elections campaign, we exposed a random sample of French voting-age Facebook users to false statements by a far-right populist party. A randomly selected subgroup was also presented with fact-checking of these statements; another subgroup was offered a choice of whether to view the fact-checking. Participants could then share these statements on their Facebook pages. We show that (i) both imposed and voluntary fact-checking reduce sharing of false statements by about 45 percent, (ii) the size of the effect is similar between imposed and voluntary fact-checking, and (iii) each additional click required to share false statements sub stantially reduces sharing. (JEL D72, D81, D91)