Guide
Where is the serial number on a bike?
On most bikes, the serial number is engraved under the bottom bracket: turn the bike over and look between the pedals, underneath. If it is not there, check the head tube (the front of the frame, below the handlebars), the rear stays or dropouts, the bottom of the seat tube or a sticker on the frame. It is usually on the receipt too. On e-bikes, the motor and the battery have their own numbers. Write it down, take a photo and register it: it is what the police will ask for if your bike is stolen.
Reviewed in October 2026.
Step by step
Look under the bottom bracket
Turn the bike upside down or lay it on its side and look at the underside of the part the pedal axle goes through. This is the most common spot for most brands. If it is dirty, wipe it with a damp cloth before reading it.
If it is not there, check the rest of the frame
Other common spots are the head tube (at the front, below the handlebars), the rear stays and dropouts (where the rear wheel is attached), the bottom of the seat tube and the underside of the down tube. Some brands use a sticker, often white or with a barcode, instead of an engraving.
Read it carefully
Copy every letter and number in the same order. Some characters are easy to mix up, such as 0 and O or 5 and S: if in doubt, compare it with the receipt. If there are several groups of characters, write them all down. Do not confuse it with model, size or frame maker codes.
Take a photo
In good light, or with your phone torch held at an angle so the engraving casts a shadow, take a close-up photo where it can be read clearly and another from further away showing where it is on the frame. Keep them with the receipt and photos of the whole bike.
On an e-bike, note the motor and battery numbers too
The motor and the battery have their own serial numbers, usually on a label. The battery number is usually visible when you take it out of its mount; the motor number, depending on the model, from underneath or after removing a cover.
Motor and battery numbers on e-bikesKeep it safe and register the bike
Keep the number somewhere you will not lose it and register the bike: on destolen, registration is free (up to 5 bikes) and you can store the frame, motor and battery numbers with photos. If your bike is stolen, you will have them ready for the police report.
Differences by type of bike
On road, mountain and city bikes it is normally under the bottom bracket. According to Bike Index, some brands engrave it on the head tube, and on some BMX and older bikes it is on the rear dropout.
On e-bikes with a mid-drive motor, the bottom bracket is usually covered by the motor, so the frame number goes elsewhere. Riese & Müller, for example, says that depending on the model it may be above the motor on the drive side, at the bottom of the seat tube, under the down tube, under the battery or on a sticker; Cannondale usually puts it under the bottom bracket.
Handmade bikes and some very old ones may have no serial number. In that case, keep the receipt and photos of the details that make it unique.
What to do if the number has been removed or cannot be read
If it is your bike and the number has worn away, look for it on the receipt, the warranty certificate or the owner's manual (some brands record it in a bike passport at the end). If you do not have it, ask the shop where you bought it or the manufacturer, with your proof of purchase.
If you are about to buy a bike and the number has been filed off, scratched or covered with paint or stickers, do not buy it: it is a warning sign. You can tell the police and give them the link to the listing.
Frequently asked questions
Do all bikes have a serial number?
Almost all. According to Bike Index, the ones without one are usually handmade or very old bikes. If yours has none, keep the receipt and photos of its details.
What is a bike serial number for?
To identify the bike beyond doubt: the police ask for it in a theft report, stolen bike registries use it to look for the bike and, before buying a used bike, it lets you check for free whether it is reported stolen.
Sources
Have your bike's details ready
Register your bike for free with photos and serial number: if it is stolen, you will have everything at hand to report it and search for it. And before buying a used one, check its serial number.