Many technology pundits say that Web and mobile applications that are tailored to where you are — often called “location-based services” — will be the next big thing. Or at least, one of the next big things.

Before those applications take off, however, some problems must be solved. For example, there are already several services that track a user’s location, but many applications that want to access that information have no easy way to get it. For their part, users want to decide which applications can have access to their location information and which cannot — and they want to do it once, if possible.

On Tuesday, Yahoo introduced a new service called Fire Eagle that simplifies all that. It is free and available to any application and any user who wants to try it.

“We really wanted this functionality for Yahoo’s services,” David Filo, a Yahoo co-founder, said to reporters in San Francisco. By opening it up to everyone, the service will probably gain much wider adoption, Mr. Filo said.

At this point, more than 50 third-party applications from partners like SixApart, which offers a blogging platform, and Pownce, a micro-blogging service, are using Fire Eagle.

“We can bring the same functionality to Yahoo properties,” said Tom Coates, head of product at Yahoo Brickhouse, a home for start-up-like projects within Yahoo.

The service appears to give users complete control over which applications have access to their location. Users can also control whether an application can track their exact location, their ZIP code or merely the city they are in, for example. And they can purge any personal information from the system when they want to.

Yahoo will not make any money from Fire Eagle, at least for now. Mr. Coates raised the possibility that the service would be linked to advertising applications that want to know a user’s location in the future.