Their services were no longer required in the age of artificial intelligence.
"So that's how 16 years ends, not with a big goodbye and a party, but a morning email," James Winters, a Sydney-based software engineer for Atlassian, posted on LinkedIn.
"So time to dust the gardening gloves off, then."
All of Atlassian's 14,500 employees in 14 countries were told to be on standby for the email, a message they were told they would receive within the next 20 minutes, laying out whether they still had a future with the company.
Another Sydney-based Atlassian employee, product designer Sophie Matrai, was let go on Thursday, 200 days into her maternity leave.
"Being on mat leave, facing a rising mortgage and raising two kids in Australia without family is a massive challenge," she wrote.
Other laid-off workers posted how grateful they were for their time at the company, how they had worked on tough problems with smart, cool people and that they were proud of what they accomplished.
Software engineer Luciano Leggieri said he hoped to find another tech job in the San Francisco Bay Area before his work visa expired.
"Otherwise, I'll continue the search back in Sydney," he wrote.
In all, 1600 Atlassian employees received the dreaded notification - 10 per cent of its global workforce.
Thirty per cent of the affected employees were based in Australia, a spokeswoman said. That's 480 jobs.
In a video message to staff, Atlassian chief executive Mike Cannon-Brookes said it was a very tough day for the company.
"I don't make decisions like this lightly," he said.
"I know there are real consequences for everybody, their families, their career plans, their friendships."
The increasing adoption of artificial intelligence drove the decision, he said.
Mr Cannon-Brookes said Atlassian's approach was not AI replacing people, but it did change the mix of skills and the number of roles required in certain areas.
Atlassian continues to hire even as it lays off employees, advertising on Wednesday for 108 different positions.
The software giant said the laid-off employees would receive a minimum of 16 weeks of pay and an extra week for each year of service, with health care plans extended for six months.
Rajeev Rajan would also step down as chief technology officer, Atlassian said.
He will leave on March 31 after almost four years with the company, which makes a suite of cloud-based collaboration tools used for software development and project management.
Atlassian's new global headquarters, a 39-storey hybrid timber tower, is under construction next to Central Station in a new tech precinct.
Other tech companies have also cited AI's impact on staff cuts, including Australia's Wisetech Global, which in February said it would reduce its global workforce by more than 2000 jobs.
Afterpay owner Block, Oracle, Commonwealth Bank, Amazon, Salesforce, Pinterest and CrowdStrike have also mentioned AI in justifying layoffs.
"There's no doubt we are seeing a structural reset of the workforce," CEO of business services company TP in Australia Miranda Collard said.
In February, the Sydney-headquartered software company reported $US1.6 billion ($A2.3 billion) in revenue for the three months to December 31.
This was up 23 per cent from a year ago and ahead of expectations.
But its net loss for the second quarter widened to $US42.6 million ($A61 million), up from $US38.2 million ($A54.7 million) a year ago.
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