In recent years, law enforcement officers have employed so-called geofence warrants to obtain information that technology companies collect about their users’ cell-phone locations. Suppose that investigators know a crime was committed at a particular place and time, but do not have a suspect. They may draw a “geofence”—a virtual perimeter—around the crime scene and get a warrant compelling a company to hand over data about the cell phones located in that area near the time of the crime. Following a process specified in the warrant, the company will turn over the cell-phone data and eventually identify by name one or more of the users thus disclosed.
The geofence warrant at issue here was directed to Google, and used to solve a bank robbery. Hundreds of millions of Google users have activated a service called Location History, which records the location of a user’s cell phone every two minutes or so. Through a geofence warrant, police officers required Google to turn over Location History data revealing cell phones within the vicinity of a bank at around the time it was robbed. At the end of the multi-step process described in the warrant, Google gave the police three names. The Federal Government soon charged one of the individuals thus identified, petitioner Okello Chatrie, with committing the crime.
Today, we consider how the Fourth Amendment applies to that use of a geofence warrant. Answering that question in full would mean deciding whether the police conducted a Fourth Amendment “search” when they acquired the cellphone data leading to Chatrie’s arrest and, if so, whether that search was reasonable given the features of the warrant they employed. We decide the first part of that inquiry today, concluding that the police conducted a search when they gained access to Location History data. An individual has a reasonable expectation of privacy in records about his cell phone’s location, and police intrude on that constitutionally protected interest when they demand the information—even though for only a limited time, and from a third-party tech company. We leave to the Court of Appeals the further question whether, given the warrant issued, the search here was reasonable, meaning that each of its steps was properly described with particularity and found to be supported by probable cause.
We granted certiorari solely on the question whether the police violated the Fourth Amendment in obtaining Chatrie’s location data, thus declining to consider the exclusionary rule issue. See 607 U. S. 1148 (2026). The disputed Fourth Amendment question divides into two parts. First, did law enforcement officials conduct a search under the Fourth Amendment when they acquired Chatrie’s location data from Google? We hold that they did because an individual has a legitimate expectation of privacy in his cell-phone location data. Second, did the multi-step geofence warrant issued here make that search reasonable? We leave that question—which requires deciding whether the warrant satisfied the Fourth Amendment’s probable cause and particularity requirements at each stage of the search process—to the Court of Appeals to address in the first instance.
Whatever the form of an attempted incursion, the Fourth Amendment protects Americans’ long-held conviction that no government official should have free access to the most closely kept aspects of their lives.
Contrary to the Government’s view, an individual has a legitimate expectation of privacy in the information Location History collects about his cell phone’s—meaning his own—movements. The police invade that expectation, and thus conduct a search, when they acquire that information, even though for only a limited period of time and even though via a third-party tech company.
Location History resembles other private materials—think of emails, documents, photographs, or calendars—that even if stored on Google’s servers, a user reasonably views as his own. And as a result, that he reasonably expects to be shielded from the “inquisitive eyes” of the government.
The Government replies with an odd argument. It thinks that “tracking [someone] into a private residence”—yes, even for two hours—would “probably” be a search, but tells us not to worry because Chatrie did not go home. Tr. of Oral Arg. 98, 134. That approach, however, is foreign to the way the Fourth Amendment works. Whether something is a search does not depend on what it finds. See Di Re, 332 U. S., at 595 (“[A] search is not to be made legal by what it turns up. In law it is good or bad when it starts”). An officer, after all, cannot know the fruits of a given surveillance in advance. The surveillance must be either a search or not regardless. The Government’s concession thus gives away its argument that, for purposes of the Fourth Amendment, two hours of cell-phone location data is not enough.
Location History is even more “revealing” than CSLI, because it provides a yet more precise record of an individual’s movements. See supra, at 16–17. Access to that record enables officials to undertake nearly perfect, retrospective surveillance of countless persons and places. See supra, at 17–18. And for Location History, that surveillance is based on information that a user reasonably understands as his own, even though stored on Google’s servers—much like his emails, photos, and calendar entries. See supra, at 18. Likewise, the information is “not truly shared,” in the normal sense of wanting a third party to see or use it. Carpenter, 585 U. S., at 315. The exposure of that information to Google is merely what happens when a user avails himself of one of the services on his cell phone. Or said a bit differently, it is the automatic price of conventional cellphone usage—which, just as Carpenter noted, is a “pervasive and insistent part of daily life.” Ibid. So just as the third-party doctrine did not apply in Carpenter, it does not apply here.
For all those reasons, we hold that police officers invade a cell-phone user’s reasonable expectation of privacy when they access his Location History. It does not matter if the time period scrutinized was only two hours. Nor does it matter that the materials obtained were handed over by a third-party tech company. When the government “accesses historical cell phone” location information—Location History as much as CSLI—it “conducts a search under the Fourth Amendment.”
That conclusion does not resolve this case, because the Fourth Amendment prohibits only searches that are “unreasonable.” When law enforcement officials undertake a search to discover evidence of a crime, the reasonableness standard generally requires that they seek a warrant from “a neutral and detached magistrate.” Johnson v. United States, 333 U. S. 10, 14 (1948); see Vernonia School Dist. 47J v. Acton, 515 U. S. 646, 653 (1995).11 That requirement subjects the officials’ assessment of a search’s propriety to the “deliberate, impartial judgment of a judicial officer.” United States v. Grubbs, 547 U. S. 90, 99 (2006). The magistrate, in turn, may issue a warrant only when “probable cause is properly established and the scope of the authorized search is set out with particularity.” Kentucky v. King, 563 U. S. 452, 459 (2011).
“[P]robable cause is a fluid concept—turning on the assessment of probabilities in particular factual contexts—not readily, or even usefully, reduced to a neat set of legal rules.” Illinois v. Gates, 462 U. S. 213, 232 (1983). But a magistrate must always determine that there is a “fair probability that contraband or evidence of a crime will be found” in the place searched. Id., at 238. That means determining, to the requisite “fair probability,” both that the place searched will have the materials sought and that those materials will contain evidence “aid[ing]” in a criminal’s “apprehension or conviction.” Messerschmidt v. Millender, 565 U. S. 535, 551, 552, n. 7 (2012); see Zurcher v. Stanford Daily, 436 U. S. 547, 556 (1978) (“The critical element” is whether there is the requisite “cause to believe that the specific ‘things’ to be searched for and seized are located” in the targeted place). The particularity requirement, for its part, ensures that the search will be of an appropriate scope—that it is “carefully tailored to its justifications, and will not take on the character of the wide-ranging exploratory searches the Framers intended to prohibit.” Maryland v. Garrison, 480 U. S. 79, 84 (1987). That requirement typically looks to such matters as the geographic and durational expanse of the search. See id., at 84–85; Karo, 468 U. S., at 718. And it too must take account of “particular factual contexts,” including in surveillance cases the nature of the technology to be used.
In his famed and vindicated dissent, Justice Brandeis explained why a wiretap was a search, subject to Fourth Amendment requirements. See Olmstead v. United States, 277 U. S. 438, 471 (1928). Those who drafted the Amendment could not have imagined such a technology. But they understood, Justice Brandeis wrote, a matter of more transcendent importance: that Americans had “as against the Government, the right to be let alone” and that the Fourth Amendment must protect against “every unjustifiable intrusion by the Government upon the privacy of the individual, whatever the means employed.” Id., at 478.
Far more recently, this Court in Carpenter invoked Justice Brandeis’s opinion in explaining why law enforcement officials could not have “unrestricted access to a wireless carrier’s database of physical location information.” 585 U. S., at 320. Said Carpenter: “[T]he Court is obligated—as ‘[s]ubtler and more far-reaching means of invading privacy have become available to the Government’—to ensure that the ‘progress of science’ does not erode Fourth Amendment protections.” Ibid. (quoting 277 U. S., at 473–474 (dissenting opinion)). For new technological tools, the Court continued, may “risk[] Government encroachment of the sort the Framers, after consulting the lessons of history, drafted the Fourth Amendment to prevent.” 585 U. S., at 320.
Today’s decision follows from the same judicial obligation, to guard against the same risk of undue encroachment. The Fourth Amendment applies, too, when officials tap into Google’s “database of physical location information.” Ibid. That database is new, but the principle covering it is not: That principle is instead the one our history has given. The Fourth Amendment must, as ever, protect against unjustified governmental intrusion on the privacy of the individual.