Activists, celebrities and journalists joined a boycott of Twitter on Friday to protest the social media platform’s locking of the account of the actress Rose McGowan, a fierce critic of the film producer Harvey Weinstein over his alleged sexual harassment and assaults of women.

The boycott began at midnight Thursday in New York and was to last all day. Many of those taking part signified their participation with the hashtag #WomenBoycottTwitter.

Heidi Moore, an editor, was among the first to popularize the campaign, writing on Twitter, “Friday October 13th seems a good boycott day.”