Carfax is a useful tool. We recommend every used car buyer pull one before purchasing. But there is a widespread and dangerous misconception that a clean Carfax means a clean car.
It doesn't.
What Carfax Shows
Carfax compiles data from insurance companies, DMVs, police reports, and some repair shops. When an accident is reported through one of those channels, it shows up. When a title is branded as salvage or flood damaged through official channels, it shows up.
What Carfax Doesn't Show
Any accident that wasn't reported through official channels — and that is a very large category. A fender bender handled privately between two drivers, cash payment at a body shop, never appears. A vehicle repaired at an independent shop that doesn't report to Carfax's network never appears. Industry estimates suggest a significant percentage of accident-damaged vehicles on the market have no reported history whatsoever.
What a Physical Inspection Finds That Carfax Cannot
A paint thickness gauge measures the depth of paint on every panel of the vehicle. Factory paint has a consistent, predictable thickness. A repainted panel reads differently. There is no database that can tell you this — only a gauge pressed against the metal.
Panel gap analysis identifies panels that don't sit the way they did from the factory. Doors that don't close cleanly, fenders with uneven spacing, hood lines that don't match — these are signs of structural repair that no history report captures.
A full multi-module diagnostic scan reads every computer in the vehicle. Sellers who know how to clear codes do so before listing. But stored codes and module flags often persist, and a professional scanner finds them.
The bottom line is simple. Carfax tells you what was reported. A JAG inspection tells you what's actually there. Use both. Never rely on one alone.