VINDecoded is the most convenient and best free app that provides a VIN check for used cars. It can also show you the detailed vehicle information and help you decide on whether you should buy a used car.

The advanced integrated VIN scanner makes it easy for you to scan the VIN barcode of a car that you want to buy. The app also displays all the information about the car and shows you a value estimate and a comparative vehicle analysis. It can also generate a vehicle history report for you.

Now, with VIN Decoded you can also get a vehicle history report for free from CARFAX.