Twitter's full-time headcount has dwindled to approximately 1,300 employees, including fewer than 550 full-time engineers by title, according to internal records viewed by CNBC.
Around 75 of the company's 1,300 employees are on leave including about 40 engineers.
The company's trust and safety team, which makes policy recommendations, design and product changes with the aim of keeping all of Twitter's users safe, is down to fewer than 20 full-time employees.
Before Musk led a $44 billion leveraged buyout of Twitter last year, Twitter's headcount stood at about 7,500 employees.
Since taking over Twitter, Musk has faced a shareholder backlash at Tesla for being distracted, for stirring up political controversy with his strategy at Twitter, and for selling billions of dollars worth of his Tesla shares to finance his Twitter takeover.