Automated license plate readers
Automated license plate readers (ALPRs) are high-speed, computer-controlled camera systems that are typically mounted on street poles, streetlights, highway overpasses, mobile trailers, or attached to police squad cars. ALPRs automatically capture all license plate numbers that come into view, along with the location, date, and time. ALPRs may also capture distinguishing features of a vehicle, including the color, make and model, augmentations, damage, and even bumper sticks. All of this data, which includes photographs of the vehicle and sometimes its driver and passengers, is then uploaded to a central, searchable database. Law enforcement can search the data based on a license plate number or a location; they can even run a search based on a vehicle’s characteristics without entering a license plate number.
Vendors say that police can use information collected to find out where a plate has been in the past, to identify which vehicles were near a particular location, to identify travel patterns, and even to discover vehicles that may be associated with another. Law enforcement agencies can choose to share their information with thousands of other agencies through nationwide networks.
Taken in the aggregate, ALPR data can paint an intimate portrait of a person’s life—where they live and work, who they associate with, and when they visit sensitive locations such as health centers, immigration clinics, gun shops, union halls, protests, or centers of religious worship. They can also be used to track individuals who happen to catch law enforcement’s attention for any reason, as illustrated by the dozens of cases in which police have used them to follow current or former romantic partners or rivals.
Drivers have no control over whether their vehicle ends up in an ALPR database because the government requires all car, truck, and motorcycle drivers to publicly display license plates. This is why ALPRs are a mass surveillance technology: they track and record the movements of everyone on public roadways, without suspicion that they are connected to any crime.
How ALPR Systems Are Comprised
ALPR systems are composed of ALPR cameras and a searchable central database.
ALPR Cameras
ALPR cameras can be broadly divided into three categories.
Stationary or Fixed ALPR cameras
Stationary or fixed ALPRs are installed in a fixed location, such as a traffic light, a telephone pole, the entrance of a facility, or a freeway exit ramp. Many vendors will install dedicated standalone poles with solar panels for the devices. These cameras generally capture vehicles that pass within view.
If multiple stationary ALPR cameras are installed along a single thoroughfare, the data can reveal the direction and speed at which a car is traveling. With enough cameras, police can track a vehicle in real time. If the data is stored over time, it can reveal every time a particular plate has passed a given location, allowing police to infer where a driver lives or works. Smaller municipalities often install ALPR cameras at the entrances and exits to the town, creating a virtual gated community no one can visit without being documented. EFF found this in Tiburon, CA, a town of just over 9,000 people, with one of the largest ALPR data collections in the state at the time.
Police will sometimes disguise ALPRs as mundane objects, such as traffic barrels or cacti.
Mobile ALPR Cameras
Mobile ALPRs are often attached to police patrol cars, allowing law enforcement officers to capture data from license plates as they drive around the city. In addition to capturing images of passing vehicles, mobile ALPR cameras are effective at capturing license plates of parked cars. For example, a patrol car may drive around a public parking lot capturing hundreds of vehicles’ plates in minutes.
Police can also use ALPRs for "gridding," which involves a vehicle with a mobile ALPR systematically driving up and down every block of a neighborhood to capture all license plates in hopes of solving future cases.
Private vendors such as Digital Recognition Network, a subsidiary of Motorola Solutions, also contract with repossession companies to capture plate data using mobile ALPRs. The company then sells that data to law enforcement agencies, including U.S. Immigration and Customs Enforcement (ICE), as well as to commercial industries, such as insurance companies and private investigators.
ALPR Trailers
ALPRs are also available as trailers that police can tow to leave in a particular area for extended periods of time. ALPR trailers collect data in a similar fashion as fixed ALPRs, but without police having to permanently install the cameras. They often take the form of trailers with speed warnings.
ALPR Databases
All of the data that a city’s ALPR cameras collects is sent to a searchable central database.
While police departments may host their own ALPR databases, typically, they are hosted by private companies such as Motorola Solutions or Flock Safety. Law enforcement agencies without their own ALPR cameras can access data collected by other law enforcement agencies through regional or national sharing networks operated by these private companies. Some of the most common ALPR data networks include:
- Flock Safety. Flock Safety boasts database features that allow for agency-to-agency sharing with law enforcement across the country. Flock also offers a product called NOVA that connects ALPR data to other data sources.
- Motorola Solutions’ National Vehicle Location Service NVLS)/LEARN. This database allows law enforcement agencies access through Motorola’s system and third-party investigative platforms, such as Thomson Reuters CLEAR.
- National License Plate Recognition Program. The U.S. Drug Enforcement Administration (DEA) operates a database that integrates ALPR data collected by federal agencies, as well as partner local and state agencies.
- Nationwide LPR Pointer Index. This database is operated by the National Law Enforcement Telecommunications’ System (Nlets), which allows for law enforcement searching of ALPR systems across the U.S. As noted above, several companies operate independent, non-law enforcement ALPR databases that sell the information to private entities like insurance companies and private investigators, but law enforcement can also purchase access to this commercial data on a subscription basis.
These databases retain ALPR information for varying lengths of time and are set by each agency. Retention periods range from as short as three minutes to as long as several years, although some entities—including private companies—may retain the data indefinitely.
How Law Enforcement Uses ALPR Technology
ALPR data is gathered indiscriminately, collecting information on millions of ordinary people. By plotting vehicle times and locations and tracing past movements, police can use stored data to paint a very specific portrait of drivers’ lives, determining past patterns of behavior and often even claiming to predict future ones, in spite of the fact that the vast majority of people whose license plate data is collected and stored have not been accused of a crime.
Law enforcement has two general purposes for using license plate readers: real-time investigations (i.e., hotlists) and historical or retrospective investigations.
Real-time Investigations (i.e., Hotlists)
Law enforcement agencies will often pre-load a list of license plates that the ALPR system is actively looking for, such as stolen vehicles or vehicles associated with outstanding warrants, into a “hotlist”. If the ALPR camera scans a plate on the hotlist, the system sends an alert to the officer in the squad car (if it's a mobile reader) or the agency (if it's a fixed reader).
Hotlists range in the types of offenses that are included and who has oversight of them. In many departments, police officers can also create their own hotlists with little to no oversight. Some include low-level misdemeanors and traffic offenses. ICE maintains a national “immigration violator” hotlist through the National Crime Information Center, which hundreds of local law enforcement agencies employ, including departments that maintain policies prohibiting assistance for immigration enforcement. Some agencies have used hotlists to generate revenue by identifying and stopping individuals with outstanding court fines.
A 2021 report by EFF found that according to data from 63 law enforcement agencies in California, only 0.05% of the data collected by ALPRs was relevant to a public safety interest (i.e., a hotlist) at the time the data was captured.
Training materials, policies, and laws in some jurisdictions instruct officers that a hotlist alert on its own may not be enough to warrant a stop. Officers are instructed to visually confirm that a plate number is a match. Failure to manually confirm, combined with machine error, has caused wrongful stops.
Historical or Retrospective Investigations
Since ALPRs typically collect information on everyone—not just vehicles on a hotlist—officers can use a plate, a partial plate, vehicle descriptors, or a physical address to search and analyze historical data. For example, an officer may enter the location of a convenience store to identify vehicles seen nearby at the time of a robbery. The officer can then look up those plate numbers to find other locations those plates have been captured.
Police do not obtain a warrant prior to searching ALPR databases for historical investigations. This means that law enforcement can conduct searches of their own accord, without showing probable cause or any suspicion at all prior to conduct a search. Publicly released audit logs show that agencies often engage in extensive searches of their ALPR data. For example, the San Jose Police Department conducted 261,711 searches of its ALPR database in just over a one-year period between June 5, 2024 and June 17, 2025.
Data Sharing & Sharing Networks
When an ALPR camera captures a vehicle, the data often does not remain solely with the local law enforcement agency. Modern ALPR systems, like Flock Safety’s, feed ALPR information into cloud-based databases that allow for instantaneous, automatic, and continuous sharing among law enforcement agencies, as well as sharing from private ALPR customers with law enforcement. This sharing can take the form of nationwide sharing networks, regional or statewide sharing networks, or one-to-one sharing with specific agencies.
Once a sharing partner or network is selected, agencies automatically and continuously share all ALPR data captured with those partners, as long as sharing remains turned on. This sharing is different in kind from traditional cooperation between agencies collaborating on a specific case; it involves shared access to a single database, running continuously, transforming a local surveillance program into a node in a vast, interconnected network.
To illustrate the scope of sharing, during the same time period that San Jose Police Department searched its ALPR database over 261,711 times (as identified above), California agencies listed as sharing partners searched San Jose’s database nearly 4 million times.
Border Surveillance
ALPRs are one of the ways that federal agencies monitor vehicle traffic along the U.S.-Mexico border. EFF maintains a map of ALPRs at checkpoints and land ports of entry, as well as covert ALPRs in Arizona and California.
Checkpoints
U.S. Customs and Border Protection (CBP) and its subagency U.S. Border Patrol (USBP) operate sophisticated ALPR systems at most checkpoints and land ports of entry. These systems collect multiple images of a vehicle from all sides. The data is stored for 15 years, although officials are typically only able to search the most recent five years of data. The DEA operates a parallel ALPR system near USBP checkpoints. The general rule of thumb is that if you are driving away from the border, you will pass a USBP ALPR system, but if you’re traveling toward the border, the DEA will be monitoring your traffic. Regardless, these systems feed into the same National License Plate Reader Program database maintained by the DEA.
Covert ALPRs
Both USBP and DEA operate a network of covert ALPRs along the border. These cameras may be disguised as traffic barrels or trailers. The data captured by these ALPRs is maintained for two years.
Combining ALPR Data with Other Data Streams
ALPR data is often regularly added to a centralized platform at local real-time crime centers that allow it to be combined with other data. Increasingly, ALPR vendors are involved not just in the selling of ALPR systems, but also other surveillance technologies that integrate ALPR data with other data streams to provide more granular data on people’s movements. For example, Axon operates Fusus, a “rapidly deployable real-time crime center in the cloud” that pulls in data from sources such as body-worn cameras and drones, in addition to ALPR systems.
Who Sells ALPR Technology
Motorola Solutions and Flock Safety are two of the most common ALPR vendors in the United States. Other vendors include Axon, Elsag, Rekor, SoundThinking, Insight LPR, and Jenoptik. Increasingly, the interoperability between companies as well as the growing trend of companies creating products that populate the entirety of the surveillance process, i.e. collection, analysis, storage, fusion, and sharing, means that many of these companies that sell ALPR services also sell other surveillance products designed to increase the utility and insights that emerge from ALPR data.
Flock Safety similarly has arranged partnerships with a large number of homeowners associations and private companies that that provide data to law enforcement. ALPRs also can be found in the parking lots of strip malls and other commercial properties across the country. Companies like Home Depot and Lowe's have been the target of external and shareholder activism hoping to get them to drop their contracts with ALPR vendors like Flock, whose data sharing infrastructure could enable police, including ICE, to identify individuals in the parking lots of hardware stores.
Threats Posed by ALPRs
ALPRs are a powerful surveillance technology that can be used to invade the privacy of individuals as well as to violate the rights of entire communities.
Despite ALPRs often being marketed to pursue serious crimes, police often use this technology for a wide variety of minor or non- infractions, including verifying addresses for school districting purposes and background checks. Often, the purpose of ALPR searches is not discernible because police use general search terms such as “investigation” or “suspect,” without further detail. In some cases, officers provide no legitimate justification for searches, typing into the reason field “LOL,” “idk,” or mashing keyboard buttons. Although some vendors have tried to link searches to a particular case or investigation number or require that officers select from a dropdown list of crimes, it is less clear how police ensure that the reason provided matches the true purpose of the search.
Law enforcement agencies have used this technology to surveil and collect information on marginalized communities. Police officers in New York City have targeted Muslim communities while misleading the public about the project. Police in Birmingham, United Kingdom installed ALPRs to target a Muslim community while misleading the public about the project. ALPR data EFF obtained from the police in Oakland, CA showed that police disproportionately deploy ALPR-mounted vehicles in low-income communities and communities of color. According to audit logs obtained and analyzed by EFF, more than 80 law enforcement agencies across the United States have used language perpetuating harmful stereotypes against Romani people when searching Flock Safety’s nationwide network.
There is also increasing evidence of ALPRs being used to target immigrant communities. Some ALPR vendors, like Flock Safety, claim they do not contract with immigration enforcement agencies like ICE or CBP. Nonetheless, these agencies have often obtained ALPR data related to immigrants by asking local law enforcement to run plate numbers or by going through entities such as fusion centers. One report documented local law enforcement identifying “immigration” as a reason for running a search at least 4,000 times in less than a year.
Since the U.S. Supreme Court’s overturning of Roe v. Wade, law enforcement in states with severe abortion restrictions have increasingly searched for license plates connected to people seeking or providing reproductive health services.
Moreover, dozens of police officers across the country have been reprimanded, fired, or arrested on suspicion of using ALPR databases to stalk their romantic partners or rivals. In Georgia, a police chief ran ALPR searches on his ex-partner and her teenage child over 600 times.
ALPRs also sometimes misread plates, leading to dire consequences when a vehicle is mistakenly identified as being on a hotlist. In 2009, San Francisco police pulled over a Black city worker, handcuffed her at gunpoint, and searched both her and her vehicle—all because her car was misidentified as stolen due to a license plate reader error. That encounter led the U.S. Court of Appeals for the Ninth Circuit to rule that technology alone can’t be the basis of such a stop, but that judgment does not apply everywhere, leaving people vulnerable to similar law enforcement errors. In Aurora, Colorado, a Black family, including young children, were traumatized by police after an ALPR system incorrectly identified their vehicle as a stolen motorcycle from a different state; the family ultimately settled for $1.9 million. These examples have just been the tip of the iceberg with stories continuously flowing about people being harassed by police, arrested, and even spending time jail after ALPR mistakes. A 2026 report identified that in one California town, there were inaccuracies in 71% of Flock alerts.
Apart from misreading plates, hotlists are also rife with human error. Police or private entities such as rental car companies may erroneously enter a license plate onto a hotlist or fail to remove license plates from a hotlist after a vehicle is recovered, resulting in the same types of high-risk traffic stops as described above.
Lengthy or indefinite retention periods, or combining ALPR data with other sensitive data, become more invasive and revealing, and are susceptible to both misuse and data breach. In 2019 CBP’s ALPR vendor, Perceptics, experienced a malicious cyberattack, resulting in license plates and face prints being published on the dark web.
The Fight Against ALPRs
EFF has been investigating and combating the privacy threats of ALPR technology through public records requests, litigation, and legislative advocacy since 2012.
Nationwide Contract Battles
As of October 2026, over 450 Flock Safety customers, including towns and counties across the U.S., have canceled their contracts with the ALPR company as part of a nationwide effort to fight back against invasive mass surveillance and federal use of local police digital infrastructure.
The shift is a result of three converging forces: audit findings that exposed Flock's lack of safeguards, growing community organizing pressure, and elected officials finally recognizing that saying "no" to a renewal is a viable option.
The fight around procurement, in particular, has been met with overwhelming success. When Austin, TX let its Flock pilot expire on July 1, 2025, the decision reflected a political judgment: constituents rejected a nationwide network used for immigration enforcement. It wasn't a debate about retention rates; it was a refusal to renew.
These cancellations were also acts of fiscal stewardship. By demanding evidence of efficacy, and receiving none, officials in Hays County, TX and San Marcos, TX rejected the "force multiplier" myth. They treated the refusal of unproven technology not just as activism, but as a basic fiduciary duty. In Oak Park, IL, trustees cancelled eight cameras after an audit found Flock lacked safeguards, while Evanston, IL terminated its 19-camera network shortly after. City electeds have also realized that every renewal is a vote for "vendor lock-in." As EPIC warns, once proprietary systems are entrenched, cities lose ownership of their own public safety data, making it nearly impossible to switch providers or enforce transparency later.
EFF has spent years documenting how procurement functions as a lever for surveillance expansion, from our work documenting Flock Safety's troubling data-sharing practices with ICE and federal law enforcement to our broader advocacy on surveillance technology procurement reform. The victories in 2025 and 2026 show that when cities understand procurement as political rather than technical, they can say no. Procurement power can be the most direct route to stopping mass surveillance.
As cities and counties across the country cancel Flock Safety contracts, what, if anything, will replace them remains a point of contention. While some cities move to competitors whose surveillance products pose the same threat to civil liberties as Flock, other jurisdictions, like Oconee County, South Carolina, are considering legislation that would regulate and possible prohibit all mass surveillance technologies, including ALPRs.
Litigation
In 2025, two nonprofit organizations—Services, Immigrant Rights and Education Network (SIREN) and the Council on American-Islamic Relations – California (CAIR-CA), represented by EFF and the ACLU of Northern California—sued the City of San Jose, challenging its police department’s practice of allowing officers to search its massive trove of ALPR data without a warrant. The San Jose Police Department (SJPD) uses its network of nearly 500 ALPR cameras to indiscriminately collect millions of plate scans per month. SJPD then stores these scans in a central database and allows its officers, and other law enforcement from across the state, to search it many thousands of times every month. By allowing these warrantless searches, the suit alleges, San Jose routinely violates the California Constitution’s ban on unreasonable searches and its guarantee of privacy. The lawsuit seeks a warrant requirement for historical searches. In 2026, the Wisconsin Council of Churches and a local pastor, represented by EFF and the ACLU of Wisconsin, brought a similar challenge to law enforcement’s retrospective searches of ALPR databases in four Wisconsin cities.
Outside of California, EFF has filed several amicus, or friend-of-the-court, briefs concerning ALPRs in federal appellate courts including the 4th and 9th Circuits, as well as state appellate courts in California, Virginia, and Massachusetts.
EFF has also engaged in litigation efforts on ALPR transparency and data protection. In 2013, EFF and the ACLU of Southern California sued the Los Angeles County Sheriff’s Department and the Los Angeles Police Department after the agencies refused to hand over ALPR data. The agencies claimed the records were exempt from the California Public Records Act because they were “investigative” records. This argument amounts to claiming that all Los Angelenos are under investigation, a point that both a lawyer for the LAPD and a California Supreme Court Justice agreed sounded “Orwellian” during oral arguments. In 2017, the California Supreme Court ruled in EFF and ACLU’s favor, eventually resulting in the disclosure of the ALPR data.
In 2021, local immigrant rights advocates, represented by EFF and the ACLU of California, also sued the Marin County Sheriff's Office. The case, Lagleva v. Doyle, challenged the Marin County Sheriff’s practice of sharing ALPR data with dozens of out-of-state agencies, including ICE and CBP, in violation of state laws regulating ALPR use (SB 34) and prohibiting the sharing of data for immigration enforcement (SB 54). As part of a settlement, the sheriff agreed to cease sharing data outside of California.
Accountability and Transparency Advocacy
In 2015, the California legislature passed SB 34, a bill that requires ALPR users to protect data, maintain access logs, hold public meetings before starting an ALPR program, implement a usage and privacy policy, and maintain access logs. The law also prohibits California public agencies from selling, sharing, or transferring ALPR data to out-of-state or federal agencies.
EFF has coordinated volunteers to collect ALPR policies across the state of California and to expose agencies failing to comply with the law. EFF has also independently filed public records requests with dozens of agencies to shine light on their use of ALPR data through our Data Driven and Data Driven 2 projects.
In 2019, EFF successfully advocated for the California Legislature to order an audit of several law enforcement agencies' compliance with SB 34. As a result, in 2020, the California State Auditor issued a scathing report substantiating many of EFF's concerns that agencies were not following the law, were failing to enact adequate policies, and were sharing data far too broadly.
EFF has since continued to demand California agencies stop violating the law. In 2023, along with the ACLU of Northern California and the ACLU of Southern California, EFF released public records from more than 70 law enforcement agencies in California that showed they were sharing data out-of-state. We sent letters to each of the agencies demanding they end the sharing immediately. Many complied, though some continued to violate SB 34, leading the California Attorney General to bring a lawsuit against the city of El Cajon. In 2025, EFF and the ACLU of Northern California sent a letter to the San Francisco Police Department demanding it stop illegally sharing data with out-of-state and federal agencies, including ICE. In 2026, EFF and the ACLU of Northern California sent a letter and public records request to the Marin County Sheriff’s Office, seeking an explanation for how out-of-state and federal entities got access to its ALPR system, in violation of SB 34 and the aforementioned Lagleva settlement.
EFF Legal Cases
Wisconsin Council of Churches v. Milwaukee et al.
ACLU of Southern California v. Los Angeles Superior Court (LAPD and LASD case)
Neal v. Fairfax County Police Department
Lagleva v. Marin County Sheriff
Suggested Additional Reading
EFF's Policy Position on ALPR Surveillance: Eliminate It and Reduce Its Harms (EFF)
EFF’s State Legislative Agenda to End ALPR Mass Surveillance (EFF)
Require Police to Get a Warrant to Search ALPR Data (EFF)
Are Your Local Police Using Flock Safety ALPRs to Scan for Immigrants (EFF)
Traffic Violation! License Plate Reader Mission Creep is Already Here (EFF)
She Got an Abortion. So a Texas Cop Used 83,000 Cameras to Track Her Down (EFF)
License Plate Readers for Law Enforcement Opportunities and Obstacles (RAND Corporation)
Automated License Plate Readers Threaten Our Privacy (EFF/ACLU)
The Four Flavors of Automated License Plate Reader Technology (EFF)
Things to Know Before Your Neighborhood Installs an Automated License Plate Reader (EFF)
This page was last updated on November 2, 2026.