Over the weekend, Parler shot to the top of Apple’s App Store in downloads. As of Monday, it had eight million members, nearly double the 4.5 million it had last week. Rumble said it projected 75 million to 90 million people will watch a video on its site this month, up from 60.5 million last month. And Newsmax said more than 3 million people watched its election night coverage and that its app has recently been in the top-10 daily apps downloaded from Apple’s App Store.

While social media sites marketed at conservatives have existed for years, they have often struggled to catch on more widely. Their invigoration now may add to a fracturing of the information ecosystem.

“There are real dangers around a fractured misinformation system, especially as it relates to organizing against our electoral integrity,” said Shannon McGregor, a professor at the University of North Carolina, Chapel Hill, and senior researcher at the Center for Information, Technology, and Public Life.

But Ms. McGregor said she was skeptical that any migration would lead to permanent departures from Facebook and Twitter.