The Supreme Court on Friday boosted protections for cellphone records that reveal a user’s location and movements over extended periods of time, in a major privacy decision for the internet age.

The majority, in a 5-4 opinion, required the government in most cases to obtain a warrant to get a cellphone user’s location data from phone providers because it is a search under the Fourth Amendment. The decision highlights modern-day concerns about how much personal information can be gleaned from such data.

The appeal comes from a defendant in a string of Michigan bank robberies, and is one of the more important cases of the term about protections against unlawful searches and seizures.

Federal investigators in the case obtained four months of the defendant’s cell-site location information, or CSLI, under a doctrine from the 1970s that says there is no reasonable expectation of privacy for records held by third parties, such as mobile service providers.

Chief Justice John G. Roberts Jr., writing for the majority, said the location information collected by companies is “an entirely different species of business record.”