https://www.techdirt.com/articles/20210127/14503746135/content-moderation-case-study-social-media-upstart-parler-struggles-to-moderate-pornography-2020.shtml

Summary: Upstart social network Parler (which is currently offline, but attempting to come back) has received plenty of attention for trying to take on Twitter -- mainly focusing on attracting many of the users who have been removed from Twitter or who are frustrated by how Twitter’s content moderation policies are applied. The site may only boast a fraction of the users that the social media giants have, but its influence can't be denied.

Parler promised to be the free speech playground Twitter never was. It claimed it would never "censor" speech that hadn't been found illegal by the nation's courts. When complaints about alleged bias against conservatives became mainstream news (and the subject of legislation), Parler began to gain traction.