How to Identify Any LEGO Set by Number, Photo, or Piece

Multiple methods for identifying unknown LEGO sets including our free AI scanner tool.

Every LEGO enthusiast has faced the same frustrating situation: a bin of loose bricks, a set missing its box, or a bag of pieces picked up at a garage sale with no label in sight. You know there is a real set hiding in that pile, but without a box or instructions you have no idea where to start. Identifying an unknown LEGO set is a solvable problem, and there are more methods available today than most people realize.

This guide walks through five reliable approaches to identify any LEGO set, from the fastest lookup by set number to AI-powered photo scanning and manual piece-by-piece research. Whether you are sorting a bulk lot, cataloging an inherited collection, or simply trying to track down the instructions for a childhood set, one of these methods will get you to an answer.

Method 1: Identify by Set Number

The fastest and most reliable way to identify a LEGO set is by its set number. LEGO has used a consistent numbering system for decades, and every official set has a unique identifier tied to its name, year of release, part count, and theme.

Where to Find the Set Number

On the box: The set number appears on the front of every LEGO box, typically in the bottom corner. It is also printed on multiple sides of the box for retail scanning purposes.
On the instruction booklet: Every instruction manual prints the set number on the cover, on the spine, and usually on the first inside page. Even if you only have a loose booklet, the number is there.
On the parts bag labels: Individual parts bags inside a sealed set are labeled with both the set number and the bag sequence number (e.g., "1 of 4"). If you find a sealed numbered bag without a box, the set number is on the label.
On certain bricks: Some larger or specialty bricks, particularly printed tiles and sticker-bearing panels, include part numbers but not set numbers. However, LEGO has occasionally molded set numbers directly into large baseplates.
On digital receipts and order history: If the set was purchased from LEGO's online store or a major retailer, order history records will include the set number.

How to Look Up a Set Number

Once you have the number, open LEGO's official website, Brickset, or Rebrickable and type it into the search bar. You will immediately see the official set name, the year it was released, the piece count, and the retail price. From there you can download digital instructions directly from LEGO's site for free.

Method 2: Identify by Photo with an AI Scanner

When there is no box, no instructions, and no visible set number, a photograph of the assembled model or the loose pieces is your next best option. AI-powered identification tools have made this process significantly faster and more accurate than manual searching.

The BrickLens AI Scanner analyzes photos of LEGO models and loose bricks to suggest likely set matches. Upload a clear photo of the assembled build or spread the pieces out on a flat surface and photograph them from above. The tool cross-references visual patterns, part shapes, color combinations, and known set configurations to return ranked matches with confidence scores.

Tips for Getting the Best AI Scan Results

Use good lighting. Natural daylight or a well-lit indoor surface gives the clearest color readings. Flash photography can wash out colors and make red and orange look similar.
Photograph the full model. If the set is partially assembled, try to complete it before scanning. More of the model visible means more data points for the AI.
Include distinctive parts. Unique or rare pieces are the strongest identifiers. If the set includes printed tiles, a minifigure with a specific torso, a distinctive curved hull, or a printed windshield, make sure those elements are clearly visible.
Try multiple angles. If the first scan returns uncertain results, take a second photo from a different angle or isolate the most unusual pieces and scan those separately.
For loose bulk pieces, spread them across a plain white or gray surface and photograph from directly above. The AI Scanner can often recognize sets from a spread of loose parts, particularly when distinctive printed or colored elements are present.

AI scanning is not perfect for every set, particularly very old sets from the 1970s and 1980s or sets made almost entirely of common bricks in standard colors. For those, combine the photo scan with the piece-by-piece methods described below.

Method 3: Identify by Individual Pieces

Every LEGO piece has a part number molded directly into it. This is the most granular identification method and takes more time, but it is highly reliable when other approaches fail.

Where to Find Part Numbers on LEGO Bricks

On standard bricks and plates, the part number is molded on the underside of the stud or on the inside of the bottom surface.
Technic and larger pieces often have the part number molded on an inner wall or on the underside.
Some very small pieces (1x1 tiles, 1x1 round plates) may have abbreviated numbers due to size constraints.

Using BrickLink and Rebrickable

BrickLink (bricklink.com) is the most comprehensive database of LEGO parts in existence. Enter the part number into its catalog search and you will see every set that piece appeared in, along with years of production, color variants, and current marketplace prices. If you identify three or four distinctive pieces and look them up, the overlapping set lists will quickly converge on the correct set.

Rebrickable (rebrickable.com) offers a powerful "Build from Parts" feature. You can enter a list of part numbers and quantities and Rebrickable will calculate which sets can be built from those parts, ranked by the percentage of required parts you already have. This is particularly useful for bulk lots where you suspect multiple sets are mixed together.

A Practical Workflow

Pull out the most unusual or distinctive pieces from the pile.
Look up each part number on BrickLink.
Note which sets appear across all of your lookups.
Cross-reference on Rebrickable or Browse Sets to confirm the match.

Method 4: Identify by Minifigures

Minifigures are often the fastest visual shortcut to identifying a LEGO set. LEGO produces thousands of distinct minifigures, and many are exclusive to a single set. If you have a minifigure with a recognizable torso print, helmet, or accessory, that figure can point directly to the set it came from.

How to Research a Minifigure

BrickLink Minifigures catalog: Browse by theme or search by a description of the torso print or helmet. BrickLink lists every set each minifigure appeared in.
Minifigure ID databases: Sites like Minifigure Price Guide catalog figures with photos, making visual matching straightforward.
The BrickLens AI Scanner: Upload a photo of the minifigure directly to the AI Scanner. Printed torsos with character names, team logos, or license plate-style numbers are strong identifiers.

What to Look For

Torso printing: Licensed character torsos (Star Wars, Harry Potter, Marvel, DC, etc.) are almost always exclusive to specific sets or very small groups of sets.
Head printing: Dual-sided head prints with specific expressions or character features narrow down the possibilities.
Accessories: Unique weapons, tools, or specialty helmets often appear in only one or two sets.
Leg printing: Printed legs (as opposed to plain colored legs) are relatively rare and strongly tied to specific sets or characters.

Even a plain minifigure in an unusual color combination can narrow down the time period and theme of a set. All-white spacesuits, for example, point immediately to the Classic Space theme or certain City sets from specific years.

Method 5: Identify by Instruction Booklet

A loose instruction booklet without a box is actually one of the most useful identification artifacts you can have. Instructions carry a wealth of identifying information.

Information Found on LEGO Instruction Booklets

Set number and name on the cover and inside front page
Year of publication (sometimes printed on the back cover or inside)
Part count for the complete set
Bag sequence labeling telling you how many bags the set contains
Copyright and trademark notices that help date the booklet
Back cover advertisements that show other sets from the same wave or year

If the cover page is missing but the interior pages are intact, the set number usually appears as a header or footer on multiple pages throughout the booklet.

Digital Instruction Libraries

LEGO hosts free digital downloads of instructions for the vast majority of sets ever produced at lego.com/service/buildinginstructions. If you have a set number from a partial booklet, you can download the complete official instructions immediately. Rebrickable and BrickInstructions.com also maintain extensive archives of older sets whose instructions are no longer on LEGO's official site.

Tips for Mixed and Bulk LEGO Lots

Buying or inheriting a large mixed lot of LEGO introduces an additional challenge: you may be dealing with the remains of five, ten, or twenty different sets all jumbled together. Here is a systematic approach.

Sort by color first. Group all pieces of the same color together. Sets from a specific theme tend to use consistent color palettes, and sorting by color will reveal natural groupings that suggest separate sets.

Isolate rare and specialty pieces. Pull out printed tiles, Technic panels, minifigure accessories, and any piece that looks unusual. These are your most powerful identification anchors. Look them up on BrickLink individually to find overlapping set lists.

Use Rebrickable's parts-to-sets matcher. As you identify individual parts, enter them into Rebrickable. The system will show you which sets are most represented in your inventory, helping you identify which complete or nearly-complete sets are present in the lot.

Check the Collection Calculator. Once you have identified likely sets, the BrickLens Collection Calculator can help you determine how complete each set is based on the pieces you have, and flag which parts you need to complete them.

Take inventory photographs systematically. Spread pieces from each color group on a plain surface and photograph them. These photos can be re-analyzed with the AI Scanner at any time, and they serve as a record of what you have even before you have finished identifying everything.

Be patient with common bricks. Plain 2x4 bricks in red, yellow, blue, and black appear in hundreds of sets. Do not spend time trying to trace these back to a specific origin. Focus your research energy on specialty parts, printed elements, and minifigures.

Conclusion: Start with the BrickLens AI Scanner

Identifying an unknown LEGO set no longer requires hours of manual research and cross-referencing. The five methods above cover every scenario, from a quick set number lookup to a deep dive through part databases for a bulk lot with no identifying information.

For most situations, the fastest starting point is a photo scan. The BrickLens AI Scanner was built specifically to handle the most common identification problems: assembled sets without a box, partially built models, and spread-out loose pieces. Upload a photo and get results in seconds.

When the photo scan returns multiple possibilities, use the piece-by-piece research methods to confirm the match. Start with your most unusual parts, look them up on BrickLink, and let the overlapping set lists narrow your answer down.

Once you have identified your sets, use Browse Sets to explore the full catalog and find related sets from the same theme or year. And if you are managing a larger collection or assessing the value of a bulk lot, the Collection Calculator gives you a complete picture of what you have and what is missing.

LEGO sets are built to last decades, and with the right tools, no set stays unidentified for long.