Just a few hours after Japan was devastated by an earthquake and tsunami early on Friday morning, people mobilized online to help.

Within two hours of the Japanese earthquake, a version of Ushahidi, Web software that helps people share information during a crisis, had been created by Japanese volunteers working with the Fletcher School at Tufts University. Ushahidi consists of a Web server and other software that lets anyone send in information—via a cell phone and the Web—that is then displayed on a map. The site dedicated to Japan, sinsai.info/ushahidi, is being used to pinpoint locations where people may be trapped, dangerous areas that should be avoided, and supplies of food and clean water.

Ushahidi was originally created to coordinate information relating to riots that broke out after a disputed Kenyan election in 2007. Since then the platform has been used for everything from spreading information during the Haitian earthquake in January 2010 to dealing with snow removal in New York City.

Coincidentally, before Friday's earthquake struck, Japanese volunteers had been working with Ushahidi to prepare for the possibility of an earthquake, says Patrick Meier, director of crisis mapping and new media at Ushahidi, a company founded to maintain the Ushahidi software. But Meier says the platform has become more sophisticated in the year since the Haitian earthquake. When that disaster hit, Ushahidi's development team bore the brunt of the work on its own shoulders. "It was rough," Meier says. Now it is much easier for people to create a version of Ushahidi tailored to their needs.

This year, Ushahidi has been used to help in Libya and with flooding in Australia. "Most of the time we don't even hear about a deployment until it's already out there," says David Kobia, Ushahidi's director of technology development, and Technology Review's Humanitarian of the Year in 2010.

"Ten percent of this is the technology, and the other 90 percent is the people," says Meier. "That's truer and truer as the technology gets easier to use."

To provide volunteer emergency support, Ushahidi has created a Standby Task Force—people all over the world who are trained, vetted, and ready to help with mapping all the information that pours in when an event occurs. The team now includes more than 300 volunteers.

Other Internet-based disaster-response services are following Ushahidi's lead.