What does a bike frame number look like and where is it?

Do you want to register your bike, check a second-hand bike or report a theft to the police? Then it helps to know what the frame number looks like. But which number do you need when there are several stickers and codes on your bike? And where do you start looking?

In this article we show you how to recognise a frame number, where to find it on a regular bike and an e-bike, what to do if it is hard to read and why you should save it straight away.

What exactly is a frame number?

A frame number is the identification code that belongs to the frame of your bike. Think of it as your bike's passport number. Manufacturers add it to tell bikes apart. It helps you identify the bike when you register, sell or insure it, make a warranty claim or report it stolen. In English it is also called the bike's serial number.

The number can appear on your bike in different ways:

• Stamped or engraved into the frame: the letters and digits are pressed straight into the material.
• On a durable sticker: often a white sticker with a barcode and the code in readable characters, sometimes under a protective layer of lacquer.
• On your purchase documents: on many bikes the frame number is also printed on the invoice, the warranty card or the bike passport (the card the shop gives you with the bike's details).

So a frame number tells you which bike it is, but not by itself who owns it. By registering your bike in your name in the BIKEBAZE bike registry you link the identification to your registration and the rest of your bike's details.

What does a bike frame number look like?

There is no single format that applies to every bike worldwide. What the number looks like depends on the brand, the country of origin and the year the bike was built, among other things.

The common Dutch format: two letters and seven digits

From around 2005/2006, Dutch bike manufacturers started using a more standardised way of numbering. On many bikes you will therefore recognise this structure:

• Two letters at the start, often a manufacturer or brand code.
• Seven digits after that, as the identification number.

Examples of what such a number can look like:

Please note: these are illustrative example numbers, not existing bikes you can identify with them. A brand can also use several number series.

Sometimes you will see three letters followed by digits or a different structure altogether. Bikes bought abroad, for instance in the UK, Germany or the US, often follow the manufacturer's own system. So do not rely on the number of characters alone. Look at the spot on the frame and compare the code with your purchase documents.

What does a frame number on an older bike look like?

On bikes built before 2006 the numbering was less uniform. You may come across:

• A relatively short string of digits only, such as `9876543210`.
• A combination of letters and digits of an unusual length, for example `WTU12345678`.
• A longer string, for example `WSBC12345678A`.
• A stamped code without a barcode or sticker.

On older city bikes the location of the number also varies. A short or unusual frame number is therefore not automatically suspicious. If in doubt, look for information from the manufacturer or ask a bike shop for help.

Is a frame number the same as a serial number?

In practice, frame number and serial number are often used interchangeably for bikes. Stop Heling (the Dutch police register of stolen goods) says so too: the serial number of a bicycle is its frame number. But be careful: an e-bike can have several serial numbers, for example for the battery, the motor or the display. Those are not automatically the frame number of the bike.

Do you need the number for a police report, a registration or a theft check? Then use the identification code of the frame. Do keep the other numbers separately, because they can be useful too.

Where is the frame number on a bike?

On many bikes the frame number is under or near the bottom bracket. That is the part of the frame the crank axle runs through, between the pedals. Can't find it there? Then check the other common locations.

1. Under the bottom bracket, by the pedals

This is one of the most common locations, especially on Dutch city bikes. Look at the underside of the frame, exactly where the cranks and pedals meet.

You may see a white barcode sticker or a number stamped directly into the frame.

Tip: use a torch or take a photo of the underside with your phone. You do not necessarily have to turn your bike upside down. With a heavy e-bike that is even best avoided if it is not needed.

2. On the down tube

Look at the tube that runs diagonally from the front of the bike towards the bottom bracket. The frame number can be on the underside or the side, sometimes close to the pedals.

On some brands the sticker is protected by a clear layer of lacquer, which makes it less noticeable.

3. On the seat tube

The vertical frame tube under the saddle is another possible spot. Check the lower end of this tube in particular, just above the bottom bracket, and look at the back if needed.

4. On the front fork, rear fork, head tube or top tube

Some models have the number in a less common place, for example:

• On or near the rear fork (the chainstays), close to the rear wheel.
• On the head tube, where the front fork and the handlebars meet.
• On the front fork or at another joint in the frame.
• Under the top tube, the horizontal tube between the handlebars and the saddle, on some sports bikes.

Focus on the fixed parts of the frame. A code on a removable part may be a part number instead.

5. On your invoice, bike passport or warranty card

Can't find the number on the bike? Then get out your receipt, warranty papers or digital order confirmation. Many bike shops print the frame number on these documents. The Dutch police say the same: the frame number is usually on the proof of ownership you get from the bike dealer. The seller or manufacturer can sometimes also find it in their records.

Our tip: always compare the code on your documents with the code on the frame. Especially with a second-hand purchase, it is important that they match.

Where is the frame number on an electric bike?

On an e-bike the frame number is often in the same places as on a regular bike, for example under the bottom bracket or on the down tube. But a battery, motor housing or integrated cover can block the view.

So look here first:

1. Under and next to the bottom bracket.
2. Along the down tube, including the underside.
3. At the seat tube and other joints in the frame.
4. On the purchase invoice or in the manual of your e-bike.
5. At the battery compartment, if the manufacturer says the frame number is there.

On some brands and models the frame number is behind or next to the removable battery: on a Stromer behind the battery, on a Greens on the inside of the battery cover. The exact location differs per model. Follow the manufacturer's instructions when removing the battery and never force any covers.

Frame number, battery number and motor number: what is the difference?

At BIKEBAZE you can record the details of up to three e-bike batteries alongside your bike's details. That is useful if you use different batteries or if a battery is stolen.

How do you read a damaged or barely visible frame number?

A frame number is not always clearly legible. Dirt, rust, wear and shadow can hide the characters. Here is what you can try:

1. Clean the spot carefully. Use a soft cloth with some water or a suitable mild cleaning product. Only use degreaser if it is safe for the paint or finish in question.
2. Shine a torch at an angle along the surface. With stamped characters, the side light often makes the shapes easier to see.
3. Take several photos. Photograph the number close up and from different angles. Zoom in on the photo on your phone.
4. Compare with the purchase documents. That helps you settle doubts about a `0` and an `O`, or a `1` and an `I`, for example.
5. Ask a bike shop for help. They often know where the number is on your brand and model.

On a solid, unpainted metal surface, a careful pencil rubbing on paper can sometimes make a stamped code legible. Do not do this on delicate paint, carbon or stickers.

Important: never scratch out, re-stamp or engrave letters or digits yourself. You can damage the frame number and make it harder to verify.

What if your bike has no frame number?

Not every bike has a visible or still legible frame number. This can happen with an old city bike, a home-built frame or a bike whose sticker has disappeared over the years.

First check the other possible locations and your purchase documents. If you really cannot find a number, you can still register your bike for free at BIKEBAZE. Also read: Buy a frame number sticker: protect your bike with the BIKEBAZE SafeTag. In that case, record as many recognisable details as possible: make, model, type, colour, photos, distinctive features and the purchase invoice if you have it.

Give your bike a recognisable code with a SafeTag

With a BIKEBAZE SafeTag your bike gets a unique, scannable SafeTag ID that is linked to your registration. That is also useful if the original frame number is missing or no longer legible.

A SafeTag does not replace the original factory frame number, but it does give your bike an extra means of identification. The eye-catching, tamper-resistant sticker also makes it visible that your bike is registered. Our production data from 2022 to 2026 shows that bikes with an activated SafeTag are stolen 98% less often.

Anyone who scans the SafeTag can check the status of the bike. If the bike has been reported stolen, a finder can reach the owner anonymously through BIKEBAZE.

Why should you save your frame number?

You may only think about the frame number once your bike has been stolen. But that is exactly when you do not want to be searching under your bike any more. The number is useful at several moments:

• Theft and police report: the police use the frame number to identify a stolen or found bike. The RDW bicycle theft register (the national register of the Netherlands Vehicle Authority) relies on it too: only with unique details such as the frame number can you file a complete police report.
• Recovery: a unique number helps to match a found bike with the right owner.
• Bike insurance: insurers often ask for the frame number when you take out a policy or make a claim.
• Buying and selling: you can compare the number with a receipt and transfer the registration to the new owner.
• Warranty and recalls: manufacturers and bike shops can sometimes use the number to trace the right bike or production batch.
• Prevention: by registering your bike and marking it visibly, you make it harder to resell a stolen bike unnoticed.

The Dutch police advise you to write down the frame number, keep it in a safe place, take a photo of your bike and note its distinctive features. That makes a police report and identification a lot easier.

Found the frame number? Here is how to check and register your bike

Have you found the frame number? Then you can do something useful with it straight away.

1. Check whether the bike is registered as stolen

This is especially important if you want to buy a second-hand bike. With the free BIKEBAZE bike check you search by frame number, battery number or SafeTag ID and see the status in our bike registry, at Stop Heling and at Bike Index (the international bike register) in one go.

How to do such a check step by step and what the result means is explained in Bike frame number check: how to do it in four steps.

2. Register your bike in your name for free

At BIKEBAZE, the only accessible bike registry in the Netherlands, you can register your bike in your name for free. You add the frame number and other features and can save photos and the purchase invoice. That way you have your bike's details neatly in one place and can download a proof of ownership.

Do you later buy or sell a bike that is already registered at BIKEBAZE? Then the current owner can simply transfer the registration to the new owner.

Register your bike for free at BIKEBAZE.

3. Keep your details in a safe place

Take a clear photo in which the full frame number is legible. Also take photos of the whole bike, its colour and any distinctive features. Keep your invoice as well and, for an e-bike, the battery identification.

With your BIKEBAZE registration you have all these details in one place. You can save the proof of ownership as a PDF and, with a linked SafeTag, also use it as a pass in Apple Wallet or Google Wallet.

Frequently asked questions about frame numbers

Does every bike have a frame number?

Many bikes have a frame number, but it is not visible or legible on every bike. On older bikes in particular, numbers can be in unexpected places. Look at the bottom bracket first, then check the other frame tubes and your purchase documents.

Does a frame number always consist of two letters and seven digits?

No. That format is common on many Dutch bikes since around 2006, but older bikes and international brands can have other combinations of letters and digits.

Is the barcode the same as the frame number?

No. The barcode is a way to scan information. On a frame number sticker, the number is usually printed below or next to the barcode as a readable string of letters and digits. Use that string for your registration.

Can I look up my frame number online?

If you already know the number, you can use BIKEBAZE to check whether the bike appears in the bike registry or in the theft registers we consult. If you have lost the number, first look on your invoice, bike passport or warranty details, or ask the bike shop where you bought the bike.

Does an electric bike have a different kind of frame number?

Not necessarily. An e-bike also has a frame number that belongs to the frame. The battery usually has its own identification number as well, and sometimes the motor does too. Keep those numbers separately.

Can I register a bike without a frame number?

Yes, at BIKEBAZE you can register a bike without a frame number. Add as many recognisable features and photos as possible. With an activated SafeTag your bike also gets a unique code that lets others find the registration.

How do I know if a frame number has been scratched off or tampered with?

Look for damaged metal, obvious grinding marks, painted-over sections or a code that has visibly been re-stamped. On a second-hand bike that is a reason to be extra careful. Ask for the receipt and do not buy the bike if its origin is unclear.

What should I do if my bike is stolen?

First check whether the municipality may have removed your bike to the fietsdepot (the municipal bike depot). Is it really stolen? Report it to the police and give them the frame number, the photos and as many features as possible. Report your bike as stolen at BIKEBAZE. You can do this without an account and without a previous registration. From that moment, anyone who looks up the frame number or scans the SafeTag sees that your bike is stolen. A finder can reach you and share the location, all anonymously.

Also read: How to report a stolen bike in the Netherlands (and find it).

Know your frame number? Register your bike for free

A frame number may look like an unimportant string of characters, until you need it. Fortunately, it takes little effort to look it up now. Check the bottom bracket, take a photo, save your details and register your bike.

With the free BIKEBAZE bike registry you easily register your bike in your name. Want to make your registration visible as well? Then add a SafeTag. That way you not only help yourself, but together we make it easier to recognise and recover stolen bikes.

Register your bike for free · See the SafeTag