Twitter and other big social media firms have relied heavily on contractors to track hate and other harmful content.

But many of those content watchdogs have now headed out the door, first when Twitter fired much of its full-time workforce by email on November 4 and now as it moves to eliminate an untold number of contract jobs.

Melissa Ingle, who worked at Twitter as a contractor for more than a year, was one of a number of contractors who said they were terminated without notification on Saturday.

She said she's concerned there will be an increase in abuse on Twitter with the number of workers leaving.

"I love the platform and I really enjoyed working at the company and trying to make it better. And I'm just really fearful of what's going to slip through the cracks," she said.

Ms Ingle, a data scientist, said she worked on the data and monitoring arm of Twitter's civic integrity team. Her job involved writing algorithms to find political misinformation on the platform in countries such as the US, Brazil, Japan, Argentina and elsewhere.

Ms Ingle said she was "Pretty sure I was done for" when she couldn't access her work email on Saturday.

The notification came two hours later from the contracting firm that hired her.

"I'll just be putting my resumes out there and talking to people," she said.

"I have two children. And I'm worried about being able to give them a nice Christmas, you know, and just mundane things like that, that are important.

"I just think it's particularly heartless to do this at this time."

Content-moderation expert Sarah Roberts, an associate professor at the University of California, Los Angeles, tweeted on Sunday that around "3,000+ contractor employees of Twitter were canned last night."

Twitter hasn't said how many contract workers it cut. The company gutted its communications department and hasn't responded to media requests for information since Mr Musk took over.

Contractors also do other jobs to help keep Twitter running,

"All contractors are not content moderation agents," Ms Roberts said. "Contractors fulfil many key roles inside the company. But almost all moderation agents are contractors."

In the early days after Mr Musk bought Twitter for $US44 billion ($65 billion) in late October and dismissed its board of directors and top executives, he sought to assure civil rights groups and advertisers that the platform could continue cracking down on hate.

That message was reiterated by Twitter's then-head of content moderation, Yoel Roth, who tweeted that the lay-offs on November 4 only affected "15 per cent of our Trust & Safety organization (as opposed to approximately 50 per cent cuts company-wide), with our front-line moderation staff experiencing the least impact."

Mr Roth has since resigned from the company, joining an exodus of high-level leaders who were tasked with privacy protection, cybersecurity and complying with regulations.

Sources | AP / ABC