Following Elon Musk's takeover of Twitter, some users have been jumping ship in favor of alternative social media sites such as Mastodon and Post News. But could they replace Twitter?

Mastodon is an open-source social network with microblogging features similar to Twitter and has more than one million users. Post News emerged just last month and attracts journalists and other news enthusiasts for premium content without a subscription. It has about 335,000 users. Twitter has 450 million users.

Drew Austin, tech writer at Wired, said if you look back on defunct social media sites, there is rarely ever a true replacement that follows.

"You just have to kind of live without them or replace them with something that's not really the same," Austin said on Greater Boston.

Dan Kennedy, professor of journalism at Northeastern University, said he's still on Twitter but has begun using Mastodon and Post News as well. Now, instead of checking in on one or two social media platforms, he has his eyes on several.

"We may be heading into a brave new world here," Kennedy said.

Watch: Mastodon and Post News are growing as people leave Twitter. Could they be a replacement?