# U.S. License Plate Recognition: Heimdall Adds American Plates — Decoding Per-State Formats, Recognition Fields, and the "No Unified Format" Logic

> HITech's license plate recognition now extends to U.S. plates. Unlike Taiwan's single nationwide format, the U.S. has each of its 50 states, Washington D.C., and territories issue their own plates with differing formats, colors, graphics, and slogans. By collecting real road imagery and generating large volumes of synthetic samples, we let our AI cover the major U.S. plate styles across generations and reliably read the serial number, issuing state, plate type, and registration sticker.

Published: 2026-06-05
Canonical: https://www.hitech.com.tw/en/news/2026-06-05
Publisher: Heimdall Intelligent Technology (HITech) — https://www.hitech.com.tw

Heimdall Intelligent Technology continues to expand the country coverage of its license plate recognition engine and has now officially taken on U.S. License Plate recognition. Unlike most countries with a central standard, the United States has no unified nationwide plate format; instead, plates are issued independently by all 50 states, Washington D.C., and territories such as Puerto Rico, each with different formats, background colors, graphics, and slogans. To make our AI adapt to such divergent styles, we collect real road imagery of U.S. plates to improve the model's generalization in real-world scenes, while also generating large volumes of synthetic plate samples to enrich training-data diversity, so the system can cover the major U.S. plate styles across generations.

A few facts worth noting about U.S. plates:

(1) Standard size: since 1956, U.S. states and Canadian provinces standardized passenger-vehicle plates at 6×12 inches (about 150×300 mm), the size still used across North America today; motorcycle plates are mostly around 4×7 inches.

(2) One plate or two: whether front and rear plates are both required is decided by each state; roughly half require only a rear plate, the rest require both, and a few depend on vehicle type — which directly affects whether a front-facing camera can capture a plate.

(3) Registration stickers: the U.S. mostly marks validity with annually or biennially renewed registration stickers whose colors change each year to aid enforcement, rather than replacing the whole plate.

(4) State names and slogans: plates usually carry the state name and a state slogan or graphic — e.g., Maine's "Vacationland," Arizona's "Grand Canyon State," North Carolina's "First in Flight" — and some states (such as Delaware) have long kept a distinctive gold-on-black design.

(5) Personalized plates: all 50 states and D.C. offer paid personalized/vanity plates, letting owners choose their own letter-and-number combinations within the rules.

The fields that need to be recognized on a U.S. plate are more complex than a single number string, mainly including:

(1) Serial number: the plate's primary identifier and the core of recognition.

(2) Issuing state: determining which state or territory a plate belongs to is the prerequisite for correctly interpreting the format, judged from the state name text, background color, and graphics together.

(3) Plate type: passenger, commercial, motorcycle, government, dealer, temporary (paper), disabled, vintage, tribal, military/veteran, and more.

(4) Registration sticker: month and year stickers indicating the registration's validity period.

(5) Slogans and graphics: help identify the state and avoid mistaking a slogan for the serial number.

(6) Specialty plates: U.S. states offer large numbers of special-purpose plates — for universities, the military, charities, police/fire, and government agencies — whose layouts differ from standard passenger plates. By some counts, U.S. states and territories offer more than 8,000 distinct plate designs in total, and being able to correctly distinguish specialty plates from standard ones is one of the biggest challenges in U.S. plate recognition (ALPR).

The format logic of U.S. plates varies by state with no single rule. Common examples: California uses 1ABC234 (1 digit + 3 letters + 3 digits); New York uses ABC-1234 (3 letters + 4 digits); Delaware and Rhode Island use pure digits (e.g., 123456); Connecticut and Illinois use AB-12345; one common Nevada format is 1 letter + 5 digits. Personalized plates further allow combinations outside the rules, with even less fixed length and character distribution. For a recognition system, this means no single format template can be applied — the AI must first identify the state and plate type, then read the serial number by the corresponding rule while excluding non-serial text such as state names and slogans.

The recognition challenge of U.S. plates lies in the sheer number of states and styles, the complex backgrounds of colors and graphics (scenic images, gradients, watermarks), the unfixed format of personalized plates, and the way registration stickers and slogans interfere with serial extraction. Using deep-learning models trained on both real imagery and large volumes of synthetic samples, together with image preprocessing, we recognize each of these fields reliably across different lighting and angles.

Operators with parking, residential, or traffic-management needs in the U.S., or with U.S. plate recognition requirements, are welcome to contact us — we will tailor a recognition solution to the local plate specifications and your site conditions.

## Media

- image: https://www.hitech.com.tw/images/example/usa-license-plate-1.webp