In short
On most bikes the frame number sits under the bottom bracket – where the pedal axle passes through the frame. Other common spots are the seat tube, the head tube and the rear dropout; on e-bikes it is often also shown on the motor housing. Write it down and photograph it – it is 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 stamped or engraved permanently into the frame. Without it, your bike is hard to trace after a theft – with it, it can be identified beyond doubt. Here you will learn where to find it, how to check it and how to secure it properly.
Where do I find the frame number on a bike?
There is no uniform rule about where manufacturers put the number – but a few spots are typical. It is easiest to turn your bike over or stand it on the saddle so you can reach the underside.
| Location | How likely | Note |
|---|---|---|
| Under the bottom bracket | very common | Most common spot – turn the bike over and look at the pedal axle |
| Seat tube (lower end, towards the bottom bracket) | common | Often stamped vertically |
| Head tube (front, below the handlebars) | possible | On some brands |
| Rear triangle / dropout | possible | Near the rear axle |
| Sticker on the frame | sometimes in addition | As plain text or a barcode, but it can fall off |
Wipe the spot clean – dirt and grease build up under the bottom bracket in particular. In poor light a torch helps; the characters are often only shallowly stamped.
Where is the frame number on an e-bike?
The same applies to e-bikes as above – plus one special point: the motor at the bottom bracket sometimes covers the classic spot. In that case, also check:
- the motor housing itself (which usually carries its own motor or serial number),
- the seat tube or down tube,
- the display menu of some systems (vehicle or frame data),
- the purchase documents and the manufacturer’s app.
With an e-bike it is best to note both numbers – the frame number and the motor number. That makes identification easier if the worst happens.
Frame number or serial number – what is the difference?
Short answer: on a bike, people usually mean the same thing in practice – the unique identifier of the frame. Strictly speaking, there can be two numbers:
- Frame number: stamped or engraved into the frame by the manufacturer, permanently.
- Serial number: often printed on the invoice, box or a sticker and it may be identical to the frame number – or an additional identifier used by the manufacturer.
For a police report, insurance and registration, the number permanently in the frame is what counts, because it is not so easy to remove.
How to note and secure your frame number properly
A frame number only helps if you have it to hand when it matters. Thieves are interested in the bike itself – the documented number is what helps you. Do it properly once:
- Read it off and check it character by character (0/O and 1/I are easily confused).
- Photograph it – sharp and well lit.
- Store it together with the receipt and photos, ideally digitally, so you can access it wherever you are.
- Register it: in your digital bike passport you link the number to your identity – that is your verifiable proof of ownership, EU-wide and free.
Why digital? A note in the cellar is no use to you at the station. If you register your bike with BikePass, you always have the frame number, photos and proof of ownership with you – and you can share them directly for a police report or your insurer.
You can add a visible layer with security marking – a visible code on the frame puts thieves off as well.
How do I use the frame number to check whether a bike is stolen?
This matters especially when buying used. With the frame number you can judge whether a bike has been reported stolen:
- Ask the seller to show you the frame number and proof of ownership – anyone who cannot produce either is a warning sign.
- A registered bike can be clearly assigned to its rightful owner via the proof of ownership; on a sale, ownership is transferred digitally.
- If you have doubts: walk away and involve the police if in doubt. Knowingly buying stolen goods is a criminal offence.
The other way round: a bike registered with BikePass is more attractive on resale – when you sell, you transfer the pass to the new owner in a few clicks, and the buyer gets clean proof of ownership along with it.
And if your own bike disappears: the first few hours are decisive – the guide “Bike stolen – what to do?” takes you through the 7 most important steps, and “Recovering a stolen bike” shows you the search strategy afterwards.
Quick checklist
- Frame number found (look under the bottom bracket first)
- On an e-bike, motor number noted as well
- Characters checked carefully (0/O, 1/I)
- Photo and receipt secured
- Registered digitally → proof of ownership
We write about bike theft, security marking and digital theft protection – practical, without scaremongering and with real steps you can take.
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