Cartier fakes are dominated by three pieces: the Love bracelet, the Juste un Clou nail bangle, and the Trinity ring. All three are simple shapes, which makes a passable copy easy and a perfect copy hard — the giveaways are in the metal, the engraving and the weight rather than the design.
What authenticators check: the exact font, depth and spacing of the engraved "Cartier", the serial number and the metal hallmark on the inside of the bracelet; the oval (not round) profile of the Love bracelet's functional screws and how they seat flush; the total weight, since genuine 18k gold is dense and most fakes come in noticeably light; the hallmark stamps (750 for gold, the French eagle-head assay mark, the maker's mark) and their crispness; and on watches like the Santos and Tank, the Roman numeral printing, the blued sword hands, the cabochon crown, and the movement. Serial numbers should match Cartier's format for the collection and year.
Because the decisive evidence is engraving quality, hallmarks and screw geometry — all macro-photographable — a Cartier piece can be authenticated from clear images plus a weight reading. The guides below cover the Love bracelet, Juste un Clou, Trinity and the watch lines.