Seventeen characters, no I, O or Q so they cannot be confused with 1 and 0. Split into three parts: who built it and where, what it is, and which individual unit it is.
What the parts encode
The first three characters identify the manufacturer and the country of assembly. The next six describe the vehicle - model, body type, engine, restraint system, with the exact meaning defined by the manufacturer rather than by a universal standard. The last eight identify the individual car, and include the model year, the assembly plant and a serial number.
The ninth character is a check digit computed from the others, which is why a mistyped VIN is usually detectable as invalid rather than pointing at a different car.
Why it matters more than a plate
A registration is a label attached to a car by an authority, and it changes: on sale in some countries, on transfer between regions, on a personalised plate purchase. History services key off the VIN precisely because it does not change.
With a VIN, a range of paid and free services will return service history, previous registrations, recorded mileage at various dates, accident and write-off records, and outstanding finance. Availability varies by country and some of it is legitimately public. The point is not that any single lookup is dangerous - it is that a photograph is enough to start all of them.
Where it appears in photos without anyone intending it
- Etched or on a plate at the base of the windscreen, driver's side, readable from outside.
- On a sticker in the door jamb, which turns up in interior and door-open shots.
- On service and inspection stickers in the corner of the glass.
- On paperwork photographed for a listing - the registration document, an invoice, a service book.
The last one is the least guarded. People photograph the service history to prove the car has been looked after, and the VIN, the previous owner's name and sometimes an address are all on the page.
Practical position
Cover the VIN in public listing photos and share it directly with a serious buyer who asks. That is the arrangement the information deserves: available to someone doing due diligence, not published to everyone who scrolls past.
The same applies to the paperwork shot. If you want to show a full service history, photograph the stamps and cover the identifiers, or describe it in text and offer the documents on viewing.