In short
On most bicycles, the frame number is located under the bottom bracket —where the pedal axle passes through the frame. Other common locations include the seat tube, head tube, and rear dropouts; on e-bikes, it’s often also found on the motor housing. Write it down and take a photo of it—it’s your most important proof of ownership if your bike is ever stolen.
The frame number is your bike’s “fingerprint”: a unique combination of letters and numbers that is permanently stamped or engraved into the frame. Without it, your bike is nearly impossible to trace after a theft—but with it, you can identify it with certainty. Here’s where to find it, how to check it, and how to secure it properly.
Where can I find the frame number on my bike?
There's no standard rule for where manufacturers place the number—but there are a few typical spots. It's best to turn your bike upside down or prop it up on the saddle so you can see the underside.
| Source | How likely | Note |
|---|---|---|
| Under the bottom bracket | very often | Most common location—turn the wheel over and look for it on the pedal axle |
| Seat tube (bottom, toward the bottom bracket) | frequently | Often embossed vertically |
| Head tube (front, under the handlebars) | possible | For some brands |
| Rear Frame / Dropouts | possible | Near the rear axle |
| Stickers on the frame | in some cases, in addition | As plain text or a barcode, but it may be omitted |
Wipe the area clean—dirt and grease tend to accumulate right under the bottom bracket. A flashlight can help in low light; the markings are often only faintly etched.
Where is the frame number on an e-bike?
The same applies to e-bikes as above— with one exception: Because of the motor at the bottom bracket, the usual spot is sometimes obscured. In that case, also check:
- on the motor housing itself (where you'll usually find a unique motor/serial number),
- on the seat tube or down tube,
- in the display menu of some systems (vehicle/frame data),
- in the purchase documents and in the manufacturer's app.
For an e-bike, it's best to write down both numbers—the frame number and the motor number. This makes it easier to identify the bike in case of an emergency.
Frame number or serial number—what's the difference?
Short answer: When it comes to bicycles, in practice these terms usually mean the same thing—the frame's unique identifier. Strictly speaking, there can be two numbers:
- Frame number: stamped or engraved into the frame by the manufacturer; permanent.
- Serial number: This is often found on the invoice, box, or sticker and may be the same as the frame number—or it may be an additional identifier provided by the manufacturer.
For identification, insurance, and registration purposes, the number permanently affixed to the frame is what counts, because it cannot be easily removed.
Here's how to write down and save the frame number correctly
A frame number is only useful if you have it on hand in an emergency. Thieves are only interested in the empty bike—the documented number is what helps you. Do it right the first time:
- Read the data and check it character by character (0/O and 1/I are easily confused).
- Photography —sharp and well-lit.
- Submit them along with your receipt and photos—preferably digitally—so you can access them from anywhere.
- Register: In your digital bike passport, you link the number to your identity—this serves as your verifiable proof of ownership, valid throughout the EU and free of charge.
Why go digital? A piece of paper in the basement won't help you at the train station. If you register your bike with BikePass, you'll always have your frame number, photos, and proof of ownership on hand—and you can share them right away with the police or your insurance company.
You can visibly add a bike identification code to the number—a visible code on the frame provides an additional deterrent to thieves.
How do I use the frame number to check if a bike has been stolen?
This is especially important when buying a used bike. You can use the frame number to check whether a bike has been reported stolen:
- Ask the seller to show you the frame number and proof of ownership —if they can't provide either, that's a red flag.
- A registered bicycle can be clearly traced back to its rightful owner through proof of ownership; when the bicycle is sold, ownership is transferred digitally.
- If you suspect something is wrong: Stay away, and if in doubt, contact the police. Anyone who knowingly purchases stolen goods is committing a crime.
Conversely, this means that a bike registered with BikePass is more attractive to potential buyers—when you sell it, you can transfer the pass to the new owner with just a few clicks, and the buyer receives clear proof of ownership right away.
And if your own bike gets stolen: The first few hours are crucial—the guide “Bike Stolen—What to Do?” walks you through the 7 most important steps, and “Finding a Stolen Bike” shows you the strategy for tracking it down.
Quick Checklist
- Frame number found (check under the bottom bracket first)
- For e-bikes, also note the motor number
- Characters carefully checked (0/O, 1/I)
- Photo and receipt saved
- Digitally registered → Proof of ownership
We write about bicycle theft, anti-theft coding, and digital theft protection—in a practical way, without scaremongering, and with concrete steps you can take.
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