What is an ALPR camera, and what does it actually record?

An automated licence plate reader — ALPR, sometimes ANPR outside the US — is a computer-controlled camera that photographs the licence plate of every vehicle that passes it, converts the plate to text, and records it with the time and the location.

The word doing the work in that sentence is every. This is the thing most people get wrong about them, and the thing that makes the rest of the subject make sense.

It is not looking for a car. It is recording all of them.

A traffic camera triggers on an event: you sped, you ran the light, it took your picture. An ALPR has no trigger. It photographs the car in front of it, then the next one, then the next one, continuously, and keeps every reading whether or not anyone in that car is suspected of anything.

Each reading is a small record: plate, timestamp, location, and usually a photograph of the vehicle — sometimes including the driver and passengers. Those readings are uploaded to a central server and stored.

One reading is trivial. The point is that they accumulate. Enough readings of your plate across enough cameras is a map of where you go, when, and how often — assembled without anyone deciding you were worth following.

Where they are

Fixed units on street poles, streetlights and highway overpasses. Mobile trailers that get parked at an intersection for a while. Units mounted on patrol cars, which read every plate in a parking lot as the car drives through it.

Cameras on private property count too. Homeowners' associations, apartment complexes and shopping centres buy them, and the data frequently flows to police anyway.

The "vehicle fingerprint"

Modern systems no longer stop at the plate. They log make, colour, body type and distinguishing features — a roof rack, damage, a bumper sticker. The industry calls this a vehicle fingerprint.

The practical effect, in EFF's example, is that a search need not name a plate at all. It can be run for a blue Honda CRV with damage on the passenger side door and a Georgia licence plate from Fulton County.

This matters for a specific reason: covering or altering your plate does not defeat a system that also recorded your car's colour, shape and dents. And a search by description rather than by plate is a search for a kind of person driving a kind of car, which is a different thing from looking for a known vehicle.

Who can search it

Almost always, more people than the department that installed it.

EFF's analysis of ALPR data sharing found agencies sharing with a minimum of 160 other agencies on average through one commercial network, and many sharing with more than 800 separate entities. A camera on your street is rarely a local record.

That reach is where most of the controversy sits. EFF documented Californian cities — Pasadena and Long Beach among them — appearing to share ALPR data with federal immigration authorities and dozens of other federal and out-of-state agencies after publicly promising not to.

How long is it kept?

There is no comprehensive federal law governing ALPR retention or sharing in the United States. The Congressional Research Service describes the legal position as unsettled; what exists is a patchwork of state statutes, plus whatever policy an individual department wrote for itself.

Retention windows in practice run from days to years. Some agencies have had no documented retention policy at all.

Washington passed SB 6002 in March 2026 capping retention at 21 days unless the data is needed as evidence, restricting searches to specific crime categories and banning immigration-enforcement use — an indication of where the legislative argument is going, and of how far from settled it is.

Is it legal?

Broadly, yes, on the reasoning that a plate on a public road is not private. The Brennan Center's treatment of the legal status is the useful summary: courts have generally allowed individual reads, while the question of whether aggregated long-term location data crosses a constitutional line is far less settled — and that is the question a network of thousands of cameras actually poses.

What this does not tell you

An honest list, because the confident version of this article would skip it:

• It does not tell you where the cameras are. No national registry exists.
• It does not tell you what your local department's retention policy is. That is a public records request, and the answer varies enormously.
• Vendors other than Flock sell these, and most coverage — including ours — is disproportionately about the largest one.

Finding out who runs them near you

Our free lookup takes a US town or county and returns the law enforcement agencies documented as operating Flock ALPR cameras there, from the Atlas of Surveillance, with the citation for each.

An empty result means nobody has documented an agency there yet. That is a fact about the state of the research, not a statement that your town is not covered.

Look up your town · Who the data reaches