Opera plans to officially launch Opera Mini today, though this hosted mobile phone browsing service and app has already racked up a million users.

As users browse, the Opera Mini app – designed for Java-enabled mobile phones – communicates with Opera's servers that strip down the size of websites, allowing them to load faster and fit the small screen of the phone.

The Opera app and service are free but mobile operators may charge users for connecting to the internet.

In late December, Opera quietly extended Opera Mini from being available only to residents in select European countries to being available to anyone. But at the time, Opera said the service wasn't officially available yet and could be taken down at any time. So far, around one million customers have begun using the service, said Tor Odland, a spokesman for Opera.

Interested users can download the Opera Mini application three ways, including directly from Opera's website, Opera.com, to their phones. In 30 countries, mobile users can instead send a short message to a specified number and have the app sent to them via text message. Finally, users can download the app to their computers and then transfer it to their phones.

To support the service Opera has implemented more than 100 new servers, said Christen Krogh, vice-president of engineering for Opera. He was reluctant to be more specific but said they run Linux and are massively parallel and massively redundant.

Opera is able to efficiently support the worldwide Opera Mini service by applying some of the same technologies it has developed for its browsers that are designed for small devices, Krogh said. In creating browsers for mobile phones and small devices, Opera has had to be mindful of small memory capacity and processing power. "That's something we can harvest now on the server side to prepare for the content transfer to the Opera Mini client," he said. "Since we spent so much time optimising the Opera browser, we can now serve a lot of customers without too much computing power on the server side."

Opera also sells Opera Mobile, a browser designed for smartphones that has more features than Opera Mini and operates independently of Opera's backend servers. By contrast, Opera Mini is a smaller app and is meant to bring browsing to low-end phones.

Opera is also offering Opera Mini to mobile operators and handset makers who could self-brand the browser.