Fake YSL Bag: Real vs Fake Serial, Cassandre, Stitching

Saint Laurent fails 10.5 percent of Entrupy checks. A real YSL bag carries three letters, six digits and a four digit date.

A fake YSL bag is usually caught on two things: a code that does not obey the house format, and hardware that levels the three Cassandre letters to one height. Both checks cost nothing. Both are easier to run than the photograph comparisons that fill most guides, because a format either matches or it does not.

Saint Laurent publishes almost nothing about its own numbering. So every figure on this page comes from somewhere else. Two authentication guides decode the same worked example. Four retailers publish dimensions and prices. One authentication company publishes fail rates. Each card names its source. The weak cards say so and carry a Low confidence mark.

Run the four quick checks with the bag in front of you. Then read the code and measure the width. A Loulou whose code decodes to month 00 and whose body measures square has failed twice, and the loupe can stay in the drawer.

Loulou, Kate and Sunset: What Changes Across the Line

The model decides which measurements apply, so name the bag before reaching for a ruler. The Loulou is the Y quilted chain bag, built in matelasse lambskin or calfskin over a grosgrain lining, and it is the model counterfeiters copy most. The Kate is a smaller structured flap with a Cassandre plaque on the front and a sliding chain. The Sunset and the Envelope use the same monogram plaque on a flap with a different quilt geometry. A buyer who applies Loulou dimensions to a Kate will fail a genuine bag.

The table carries an honest problem worth stating. Retailers disagree about what a medium Loulou measures. Neiman Marcus and a January 2026 price guide both give 29 x 17 x 8 cm. Net a Porter lists the medium at 30 x 27 x 12 cm, and Rebag measures one at 32 x 22 cm. The likely reason is that Saint Laurent has used the word medium across more than one body. Treat a measurement inside the band as a pass, and a measurement outside it as a question rather than a verdict.

Construction changes the checks too. The Loulou is quilted in a chevron that reads as the letter Y, a reference to the founder. Chevron symmetry and stitch tension are live checks on that model and meaningless on a smooth leather Kate. The Kate puts almost all its weight on one hardware casting, which raises the value of the Cassandre card. Every current model shares the interior code tag and the two line stamp, which is why those two cards sit at the top of this page.

One period rule cuts across all of it. The house was renamed Saint Laurent Paris in 2012 under Hedi Slimane. Bags made before that carry Yves Saint Laurent in the interior stamp and a twelve digit code with no letters. Bags made after carry the shorter name and the three letter prefix. A listing that claims 1990s provenance and shows a modern prefix has contradicted itself before any measurement is taken.

Reading the Saint Laurent Code: Letters, Style, Date

A Saint Laurent code is thirteen characters long and carries a workshop, a style and a production date. The LegitApp decode and the Luxbags guide describe the same structure and use the same worked example. Neither of them is the house, and the house confirms nothing by email.

The decode takes under a minute:

1. Photograph the tag straight on, flat, in daylight.
2. Count the characters. Thirteen in a three, six, four split, or the bag has already failed a card.
3. Read the four digits after the dot as a month and a year.
4. Check that the month lands between 01 and 12.
5. Check the year against the model. A Loulou cannot predate the Loulou.
6. Check the year against the seller. A bag bought new in 2019 cannot decode to 2023.

Then read the tag as an object rather than as a number. Both guides describe the same finish: one line, uniform font, even spacing, neatly stitched into the lining rather than glued. A code broken onto a second line is recorded as a counterfeit marker by both. So is a tag whose numbers wander off the baseline.

What the code cannot do is settle the bag. A number can be copied onto a copy as easily as it appears on an original, which is why the most common code on a good fake is a valid one. The Goyard guide on this site covers the same trap on a house that publishes even less, and the Prada serial reference covers it on one that publishes a little more. The code tells you when. The hardware and the quilting tell you whether.

Counterfeit Saint Laurent: Where the Fakes Actually Sit

Saint Laurent ranks third among the brands most likely to fail machine authentication. Entrupy put the Saint Laurent fail rate at 10.5 percent in its State of the Fake report for 2026. That sits behind Goyard at 18.9 percent and Prada at 13.1 percent, and ahead of Dior at 9 percent. Across all luxury submissions in that report, 91.9 percent came back authentic, which sets the baseline a buyer should measure against.

Read that number for what it is. The submissions behind it are bags that a dealer or a buyer already thought worth paying to authenticate, so the obvious copies never entered the sample. A Saint Laurent bag that looks right in photographs is precisely the population that produced the 10.5 percent figure. The odds are close to one in ten on the bags people are least suspicious of.

The report is harsher elsewhere, and the contrast matters for a shopper who buys across categories. Reporting on the same dataset records fail rates of 95.75 percent for Fear of God Essentials and 85.19 percent for Bape in apparel, and 54.1 percent for Louis Vuitton sneakers. Handbags are the most policed category in the secondary market and still run at one failure in ten. Apparel and sneakers run at rates that make the handbag figure look mild.

Three features of how Saint Laurent trades explain the gap between the brand and its peers. The quilted Loulou is instantly recognisable from a distance, which is what a counterfeiter sells. The house publishes no serial format, no lookup tool and no public verification service, so there is nothing for a buyer to check a number against. And the price ladder starts at 1,600 dollars for a mini, which puts the bag inside reach of a buyer who will take a risk on a discounted listing.

Border enforcement handles the import side rather than the listing side. US Customs and Border Protection runs seizures through its intellectual property rights programme, which stops infringing goods at the port. That protects the market in aggregate and does nothing for the individual parcel already on its way to a buyer who paid through a friends and family transfer.

For a shopper the practical rule is about channel rather than about brand. Saint Laurent sells through its own boutiques, its own site and a short list of authorised retailers such as the two that supplied the prices on this page. Everything else selling current season bags at a discount is either resale, where the counterparty carries the risk, or counterfeit. The Gucci bag guide on this site and the wider bags category set out the same channel logic for houses with similar exposure.

Where To Get Your Saint Laurent Loulou Authenticated

Saint Laurent does not authenticate bags for the public, and that shapes every option below. The house issues no certificates for items bought elsewhere, runs no serial lookup and keeps its verification methods internal. Anyone offering a certificate of authenticity from Saint Laurent is describing a document the house does not produce. The official Saint Laurent site is useful for confirming what a current model looks like and what it costs, and for nothing beyond that.

Machine authentication is the closest thing to a laboratory answer. Entrupy compares microscopic images of a bag against a reference library and publishes the fail rates quoted above. The service sells to businesses rather than to private buyers, so most people meet it through a dealer. Asking a seller whether a bag has been through Entrupy costs one message and often ends the conversation early.

Resale platforms with in house teams are the realistic route for most private buyers. Fashionphile, The RealReal and Vestiaire Collective inspect before or after sale and refund on a failed item, and eBay routes qualifying handbags through an inspection under its Authenticity Guarantee. None of them can query a Saint Laurent archive, because no third party has access to one. What they sell is a counterparty who absorbs the loss when a call goes wrong, and a private seller on a social marketplace cannot offer that.

Photo services sit in front of all of this, before any money moves. Services of this kind read the code layout, the stamp and the plaque geometry from your pictures and flag what does not fit. Turnaround is usually a day, and the fee is a few tens of dollars. Legitly works that tier: it pre screens a Loulou from photographs and marks the format problems, without claiming to certify the bag. No photograph can weigh 400 g of leather and chain, measure 29 cm across a quilted front, or feel whether a plaque edge is a clean step or a burr. Use the photo check to decide whether to keep talking to a seller, then run the measurements once the bag is in your hands. The Saint Laurent hub collects the related guides on this site.

Verdict: Two Failed Cards Is a Copy

Rank the checks by what they cost a counterfeiter to pass, because copies fail in that order. Printing thirteen characters onto a tag costs nothing. Stamping two lines into leather costs nothing. Cutting a body to 29 by 17 by 8 cm costs nothing. Those three cards are the ones a competent copy passes, and passing them means very little on its own.

The expensive cards are the physical ones. A Cassandre plaque cast deep enough to hold clean stepped edges, with the Y correctly proud of the S and the L, costs tooling that a copy shop does not buy. A Y chevron quilt whose stitching holds even tension across every panel costs machine time and a skilled operator. A Lampo zip that runs its full travel without a catch costs several times what a generic carriage costs. Lambskin over grosgrain that brings a medium in around 400 g costs material. A copy that passes those four is a copy that cost real money, and it will not be the one listed at 300 dollars.

So the decision rule is a count rather than a single test. One failed card on a bag that passes everything else is a reason to look harder, because retailers disagree about dimensions and hand finished goods vary. Two failed cards is a copy. A Loulou whose code runs onto two lines and whose plaque letters sit level has failed twice on the two cheapest checks on this page, and nothing further needs measuring.

One last calibration on price. Saint Laurent discounts through authorised retailers, and its bags hold value well on the secondary market. A genuine pre owned medium sits in the high hundreds to low thousands of dollars. A listing at a tenth of retail is not a find. Buy from a counterparty who carries the loss, or measure the bag yourself, and treat the bargain itself as the loudest card on the table.