Telstra on Friday revealed it has begun rolling out a WiFi offering based on Fon's hotspot sharing service.

Fon works by customers agreeing to make a small portion of their WiFi capacity publicly accessible. In return, they are granted access to other Fon-enabled hotspots, of which there are millions spread across 18 countries.

"After months of hard work, it's great to see that our network is finally expanding over Australia," said Alex Puregger, CEO of Fon, in a statement.

Telstra's Fon service is called Telstra Air, and home broadband customers with compatible home hubs will be able to activate it from next Tuesday at no extra cost.

From then on they will be able to access hotspots in residential areas, payphone sites and retail outlets in 250 towns and cities across Australia.

"We expect it will grow rapidly reaching thousands of neighbourhoods and millions of people across the country over the next five years," said Karsten Wildberger, managing director of consumer and products at Telstra.

"The network will be brought to life by us and by our customers who can enjoy greater value from their broadband service by accessing their allowance outside the home," he said.