Every car or truck since the 1981 model year has a unique 17-digit Vehicle Identification Number (VIN) filled with important details, ranging from its engine type to where it was built. The VIN is like a car's Social Security number. You need it when you register your car, buy insurance and bring it in for repairs (so the shop can order the right parts). The police will use it to identify your vehicle if it's stolen. If you are shopping for a used car, you'll need its VIN to run a vehicle history report. Finally, you can use the VIN to check for any recalls of a used car you're considering. Just put the VIN in the National Highway Traffic Safety Administration's free VIN Look-up Tool and you'll know for sure.

VINs have been used by American automakers since 1954, according to the National Highway Traffic Safety Administration, but for years, there was no standardization so they were extremely difficult to decipher. Things are much easier now, but you still need to know the format in order to make sense of those 17 numbers.

Where To Find the VIN
You can find a car's VIN in three major locations: on the driver-side doorjamb, on the firewall in the engine bay and beneath the windshield on the driver side.

Dissecting the VIN
As an example, we're using the VIN from a 2013 Cadillac ATS. Here is the VIN and its breakdown, section by section: 1G6AF5SX6D0125409

World Manufacturer Identifier (1G6) 
The first three digits make up the World Manufacturer Identifier.

• Position one represents the nation of origin, or the final point of assembly. For instance, cars made in the U.S. start with 1,4 or 5, Canada is 2, Mexico is 3, Japan is J, South Korea is K, England is S, Germany is W and Sweden or Finland is Y.
• Position two tells you about the manufacturer. In some cases, it's the letter that begins the manufacturer's name. For example, A is for Audi, B is for BMW, G is for General Motors, L is for Lincoln and N is for Nissan. But that "A" can also stand for Jaguar or Mitsubishi and an "R" can also mean Audi. It may sound confusing, but the next digit ties it all together.
• Position three, when combined with the first two digits, indicates the vehicle's type or manufacturing division. In our example, 1G6 means a Cadillac passenger car. 1G1 means Chevrolet passenger cars and 1GC means Chevrolet trucks. There have been many variations on the World Manufacturer Identifier as brands have come and gone. This Wikipedia page has a list of WMI codes.

Vehicle Descriptor Section (AF5SX6) 
Digits 4 through 9 make up the Vehicle Descriptor Section.

• Positions four through eight describe the car with such information as the model, body type, restraint system, transmission type and engine code.
• Position nine, the "check" digit, is used to detect invalid VINs, based on a mathematical formula that was developed by the Department of Transportation.

Vehicle Identifier Section (D0125409) 
Digits 10 through 17 make up the Vehicle Identifier Section.

• Position 10 indicates the model year. The letters from B-Y correspond to the model years 1981-2000. There is no I, O, Q, U or Z. From 2001-'09, the numbers one through nine were used in place of numbers. The alphabet started over from A in 2010 and will continue until 2030.

Is it confusing? Yes. So here's a list of the model years since 1981: B=1981, C='82, D='83, E='84, F='85, G='86, H='87, J='88, K='89, L='90, M='91, N='92, P='93, R='94, S='95, T='96, V='97, W='98, X='99, Y=2000, 1='01, 2='02, 3='03, 4='04, 5='05, 6='06, 7='07, 8='08, 9='09, A=2010, B='11, C='12, D='13, E='14, F='15,G='16, H='17, J='18

• The letter or number in position 11 indicates the manufacturing plant in which the vehicle was assembled. Each automaker has its own set of plant codes.
• The last 6 digits (positions 12 through 17) are the production sequence numbers. This is the number each car receives on the assembly line. In the case of our Cadillac ATS, it was the 125,409th car to roll off the assembly line in Lansing, Michigan.