Frankfurt (Germany) (AFP) – At a time of growing concern over the power of the world's mighty tech companies, one German state is turning its back on US giant Microsoft.

In less than three months' time, almost no civil servant, police officer or judge in Schleswig-Holstein will be using any of Microsoft's ubiquitous programs at work.

Instead, the northern state will turn to open-source software to "take back control" over data storage and ensure "digital sovereignty", its digitalisation minister, Dirk Schroedter, told AFP.

"We're done with Teams!" he said, referring to Microsoft's messaging and collaboration tool and speaking on a video call -- via an open-source German program, of course.

The radical switch-over affects half of Schleswig-Holstein's 60,000 public servants, with 30,000 or so teachers due to follow suit in coming years.

The state's shift towards open-source software began last year.

The current first phase involves ending the use of Word and Excel software, which are being replaced by LibreOffice, while Open-Xchange is taking the place of Outlook for emails and calendars.

Over the next few years, there will also be a switch to the Linux operating system in order to complete the move away from Windows.

The principle of open-source software is to allow users to read the source code and modify it according to their own needs.

The issue of the power wielded by American tech titans has been thrown into sharper relief by Donald Trump's return to the White House and the subsequent rise in US-EU tensions.

In the case of Microsoft, there have long been worries about the dominant position it enjoys thanks to it owning both the Windows operating system and a suite of programs found in offices the world over.

In 2023, the European Union launched an antitrust investigation against Microsoft over the way it tied Teams to its other programs for businesses.

"The geopolitical developments of the past few months have strengthened interest in the path that we've taken," said Schroedter, adding that he had received requests for advice from across the world.

"The war in Ukraine revealed our energy dependencies, and now we see there are also digital dependencies," he said.

The government in Schleswig-Holstein is also planning to shift the storage of its data to a cloud system not under the control of Microsoft, said Schroedter.

He explained that the state wants to rely on publicly owned German digital infrastructure rather than that of an American company.

Experts point to economic incentives for the sort of shift Schleswig-Holstein is making, as investing in open-source alternatives and training staff to use them often costs less than the licences for Microsoft's programs.

This is particularly the case when businesses and public bodies find themselves taken "by the throat" when hit by unexpected extra costs for mandatory updates, said Benjamin Jean from consulting firm Inno3.

Schleswig-Holstein hopes that its move away from Microsoft will eventually save it tens of millions of euros.

But organisations considering this sort of change have to reckon with resistance from staff who fear upheaval.

"If people aren't guided through it, there's an outcry and everyone just wants to go back to how it was before," warned Francois Pellegrini, an IT professor at Bordeaux University.

The potential pitfalls can be seen in the experience of Munich, whose city administration was a pioneer in using open-source programs in the 1990s.

In 2017, the city announced an about-turn, citing a lack of political support and the difficulty of interacting with other systems.

But other public bodies are staying the course: France's gendarmerie, around 100,000 strong, has been using the Linux operating system since the 2000s and India's defence ministry was in 2023 reported to have launched a homegrown system called "Maya OS".

Across the border from Schleswig-Holstein, in Denmark, reports say that the local governments of Copenhagen and Aarhus are also looking into ditching Microsoft.

Another factor that could push the trend is the EU "Interoperable Europe Act", which came into effect last year and encourages the use of open-source software.

According to Jean, "Within the space of two or three years" there could be a number of pioneer administrations who will be able to give feedback on their experiences and inspire others to make the switch.