How to find a bike frame number

A bike frame number, also known as a serial number, is a unique identifier. It’s important to record it when you get a new bike as a proof of ownership – for cycle insurance, manufacturer warranties, property databases and the police – to help should the worst happen.

Frame number location

Most typically the bike frame number can be found stamped on the bottom bracket. However, it’s not always and might not be stamped at all. It can sometimes be found on a sticker, especially with carbon frames.

Trek, for example, often has the frame number on a sticker that carries a warning message of ‘warranty void if removed’.

Note that codes you find starting with BS and EN are not what you’re looking for, they relate to safety standards and regulations.

View our handy diagram below that shows all the locations that the frame number might be found.

Bike frame number

Bike frame number examples

Typically the length is between 6 – 10 and is formed of letters and numbers.

  • Trek – often start with WTU
  • Specialized – “Specialized serial numbers typically start with the prefix “WSBC,” “WUD,” “STT,” or “STE”
  • Cannondale – will be 7 digits long
  • Brompton – located on an identification plate and are 10-digits long, near the seat clamp
  • Giant – often start with GU

If your bike doesn’t have a frame number, which is unusual, you should definitely consider registering your bike with a registration company and record all the unique aspects and photos. Choose a registration company that provides an advanced marking solution, with a tamper proof sticker. That way the police have something to match you as the owner, as you won’t be providing a frame number on the crime report.

Vintage bikes

If you ride a vintage bike, you might like to view the following useful websites. An added benefit of the research is that you might be able to work out the exact year of your bike (if not known).


  • We all remember using tracing paper at school, so take that approach if the stamped frame number is hard to read. Lay a piece of paper on top of the number and use a pencil or crayon to copy it.
  • Typically the bike shop you purchase your bike from should write down the frame number and put it on the receipt, if they don’t ask them to adjust the receipt. This will add to the provenance when you sell your bike in the future.
  • As well as recording your frame number, you should keep a record of your bike description – especially after changing parts (take photos).
  • Record your frame number and details with the bike manufacturer and on a registration database (ensuring the police have access). Some manufacturers extend warranties, as an added benefit, if you register with them – Brompton for example.

Are all frame numbers recorded in a central database?

No and there are many independent bike registration databases around the world. It’s not mandatory to register a bike (in the UK), so the uptake is low compared to the number of bikes in circulation. And whilst not to muddy the water, there have been rare cases where bike frame numbers have been found to not be unique. But as this is extremely rare, it’s fair to call frame/serial numbers unique.