The short answer
Genuine LEGO bricks usually carry the LEGO name on the studs and small part or mold numbers inside, come in consistent colors and connect with a firm, even grip. Clone bricks, made by other companies and sometimes sold as fakes in copied boxes, often miss one or more of these details. Mixed bulk lots are the most common place to find them. Some genuine pieces lack a visible logo and some clones copy details well, so check several things before deciding.
1. Look at the studs
On most standard genuine bricks and plates, each stud carries the word LEGO in raised lettering. Use good light and a magnifier. A blank stud is a common sign of a clone, but it is not proof by itself: certain small, transparent or special genuine parts may have no logo or a hard-to-see one. Lettering on clones, when present, may say another brand, look blurry or use a different style.
2. Check the inside and underside
Turn bricks over. Genuine parts often show a small part number, a mold or cavity number and sometimes a LEGO mark in the tubes or underside. Molding should be clean, with little excess plastic (flash) at the edges. Rough edges, visible injection marks in odd places and thin walls are common clone signs.
3. Inspect minifigures
Minifigures are a frequent target, because single figures from popular themes can be sought after.
- Look for small LEGO markings on parts such as the neck post, the inside of the torso, the back of the legs or the hip piece. Locations vary by era and part.
- Compare printing with official images: genuine printing is sharp and aligned, while fakes may show blurry edges, misaligned faces or colors that sit slightly off.
- Check how the arms, hands and legs move. Joints that feel loose or overly stiff are worth a second look.
4. Test colors and clutch
Genuine bricks from the same era usually match closely in color, and the plastic has a consistent finish. Clones may be slightly off-shade, too glossy or chalky. Clutch, the way bricks hold together, is another clue: genuine bricks should connect and separate with a firm, even feel. Very tight or very loose fits suggest a different maker, though worn or sun-damaged genuine bricks can also feel loose.
5. Verify the set and instructions
- Set number: find the number on the box or instructions and look it up on LEGO's official website, which hosts building instructions for many sets. The box art, piece count and theme should match.
- Box: genuine boxes have crisp printing, the official logo and legal text. Odd spelling, a slightly different logo or a theme that LEGO never released are red flags.
- Inventory: compare the parts against the inventory in the instructions, especially minifigures and printed or rare pieces. Swapped-in clone parts are common in used sets.
6. Watch for seller red flags
- "Compatible with LEGO" or "building blocks" in the fine print of a listing that otherwise looks like a LEGO set.
- Large sets or rare minifigures at a price far below what similar genuine items usually sell for.
- Stock photos only, or no close-ups of minifigures and studs.
- New sealed sets for retired themes in bulk quantities.
If you are selling LEGO
Sort out clone parts before listing, or say clearly that a lot is mixed. Photograph minifigures front and back, show the set number and instructions, and describe any missing pieces. Honest descriptions help avoid returns and disputes. If you are not sure about a few parts, list them separately or leave them out rather than guessing; buyers of genuine LEGO often check every piece.
Where WorthAI fits
WorthAI can help you identify the likely set or minifigure from a photo and see what similar genuine items sell for, with the listings behind the estimate. The estimate assumes the parts are genuine and the set is as complete as you describe it. WorthAI is not an authentication service, so sort clone parts using the checks above and ask an experienced collector or reseller if a valuable piece seems doubtful.
Frequently asked questions
Does every genuine LEGO brick have the logo on the studs?
Most standard bricks and plates do, but some small, transparent or special genuine parts have no visible logo. A missing logo is a clue, not proof.
Are clone bricks the same as fake LEGO?
Not always. Many clone brands sell openly under their own names. They become a problem when they are sold as LEGO or mixed into lots described as genuine.
How can I check if a LEGO set is complete?
Look up the set number on LEGO's official website for the instructions and parts inventory, then compare piece by piece, starting with minifigures and printed parts.
Can WorthAI tell if my LEGO is real?
No. WorthAI identifies the likely set and estimates what similar genuine sets sell for. It does not authenticate parts.