Short answer
Fake Louis Vuitton bags use polyvinyl chloride (PVC) or polyurethane (PU) coated canvas, split leather or bonded leather, polyester lining, and zinc alloy hardware with plating. Real Louis Vuitton bags use cotton canvas with a synthetic coating, full-grain cowhide leather, microfiber or textile lining, and brass or steel hardware. The material list is the first check. A 1:1 replica can use the same material classes as a real bag. Most counterfeits do not.
Coated canvas
Louis Vuitton Monogram and Damier bags use a coated canvas. The base is cotton canvas. A synthetic coating carries the print.
Counterfeit canvas is a PVC sheet with a printed pattern. PU canvas is softer and lighter. PVC canvas is stiff and has a plastic smell. A real coated canvas has a cloth back and a fine weave. The print sits under the coating. Most fake prints sit on top of the plastic. Check an inside seam allowance. Cloth fibers show on a real bag. Plastic shows on a fake.
A real coated canvas has a dry, matte surface. PVC feels slick. A PU fake flexes with less spring.
Leather trim
Vachetta is full-grain cowhide. It is untreated. It starts pale and darkens with light, oil, and time. The grain is visible. The leather flexes and returns to shape.
Counterfeit trim uses split leather with a PU coat. Split leather is the lower layer of a hide. It has no grain. Bonded leather is leather fiber mixed with a binder. It can crack at folds. Synthetic leather is plastic. It has a uniform surface and no grain.
Check a strap edge. Full-grain leather has a tight edge. Bonded leather shows fibers and binder. Check a fold. Real leather wrinkles. Plastic creases.
Lining
Real Louis Vuitton linings vary by model. Common materials are microfiber and textile. The lining is tight and even. Seams are clean.
Counterfeit linings are thin polyester satin. The fabric shines. It pulls at seams. Some fakes use thin microfiber that pills. Check the pocket seam. Loose threads and glue show on a low-grade fake.
Hardware
Real hardware is brass or steel. It has weight. The plating is thick. The logo stamp is crisp. Zippers run smooth.
Counterfeit hardware is zinc alloy. It is light. The plating is thin. It wears at corners and reveals a dull gray metal. Magnets are weak. D-rings bend. Zipper pulls feel hollow.
Stitch and edge paint
Real bags use even stitches. The thread is thick and waxed. Stitch length is consistent. Edge paint is thin and applied in layers.
Counterfeit bags use thin thread. Stitches are loose or uneven. Edge paint is one thick coat. It peels at the strap edge.
Smell and weight
PVC and glue have a sharp smell. Full-grain leather smells of leather. A real coated canvas bag has some weight from the canvas, leather, and metal. A PU fake is light. A high-tier replica can match the weight. Weight alone does not prove a bag is real.
Labels and US rules
US rules require accurate fiber content and leather labels. The Textile Fiber Products Identification Act covers fiber content. The FTC covers leather origin and material claims. Counterfeit bags often carry false labels or no material label. A seller who cannot state the canvas base, leather type, lining fiber, and hardware metal has no material spec.
What "1:1 replica" means
A 1:1 replica claim means the bag matches the real bag in material and construction. Verify four items: canvas base and coating, leather type, lining fiber, and hardware metal. Ask for a material sheet. Ask for a cut-edge photo. Ask for a hardware macro photo. A seller who gives a price and a photo set does not meet the claim.