How to Read a Serial Number [Where to Find It, 0 vs O]
Serial and model numbers are usually printed at 4 to 6 point size on a label underneath or behind a device, often stamped into metal with no ink. Zoom to 5x to 8x with your phone, angle the flashlight across stamped text to create shadows, and take a photo so you can copy the code without retyping it from memory. Check each character for 0 versus O and 1 versus I before entering it.
Where the numbers are
The serial number is the code after S/N or Serial No. on the identification label, and the model number follows Model or M/N on the same label. That label is almost always on the underside, the back, or inside a door or compartment, because manufacturers keep it off the visible faces of the product. Find it, hold your phone about 10 cm away at 5x to 8x zoom, and take a photo so you can copy the code from the image. Typical locations:
- Routers and modems: a label on the bottom with serial, MAC address, default Wi-Fi name, and often the default password.
- Laptops: the underside, sometimes under a battery or a rubber foot, and on many recent models laser-etched into the metal.
- Phones and tablets: on the SIM tray, in Settings under About, or by dialing *#06# for the IMEI. Older phones have it under the battery.
- Appliances: a rating plate inside the door frame of a washing machine or dishwasher, inside the fridge on a side wall, or on the back of an oven.
- Televisions and monitors: a sticker on the back panel, often low and near the connectors.
- Power tools and bikes: stamped into the housing, or into the underside of the frame near the pedals.
- Cars: the VIN at the base of the windshield on the driver's side, and on a plate in the door jamb.
- Watches: usually engraved on the caseback or between the lugs; see where to find a watch serial number.
Serial number, model number and the other codes on the label
A label often carries five or six codes, and support will ask for a specific one. Look for the prefix printed in front of each:
| Label prefix | What it is | Unique to your unit? |
|---|---|---|
| S/N, SN, Serial No. | Serial number | Yes |
| Model, Mod., M/N, Type | Model number: the product version | No, shared by every unit of that model |
| P/N, Part No., REF | Part or catalog number | No |
| IMEI | Mobile network identity of a phone or cellular device | Yes |
| MAC | Network hardware address | Yes |
| MFG, MFD, Date | Manufacture date, sometimes as a code | No |
| FCC ID, CE, UL | Regulatory approvals | No |
What the parts of a serial number mean
There is no universal format, but many manufacturers build serial numbers from the same pieces, read left to right:
- A letter prefix for the factory, product line or region.
- A date code, often a year digit or two followed by a week or month. Some products print the manufacture date separately; on others it exists only in the serial.
- A sequence number that counts units off the line.
- Sometimes a check character at the end to catch typing errors.
To decode a specific serial, search the manufacturer’s support site for “serial number lookup” or “find manufacture date”. Many brands publish the format or offer a lookup tool. Some newer products use random serial numbers that encode nothing, and then a lookup is the only way to learn the date.
Reading printed labels
Most labels are thermal-printed at a small point size, sometimes with a barcode, and the serial is one line among several. At arm's length it is a gray smudge. Hold your phone about 10 cm away and zoom to 5x to 8x. Tap the label to focus, then take a photo. Reading from the photo is much less tiring than reading live, especially when the label is on the back of a device you cannot easily move.
In LoupeLens, the flashlight and zoom are in the same view and a single tap focuses and captures. The photo goes to a LoupeLens album in Photos, so the next time you need the serial you open Photos instead of climbing behind the furniture again.
A photo also protects against typing errors. Zoom into the image and compare character by character as you fill in a form.
Stamped and laser-etched numbers
Serials pressed into metal, engraved on a laptop base, or etched onto a watch caseback have no ink and no contrast, and under a ceiling light they can be invisible. Light from a low angle makes them readable, because each character then casts a shadow.
- Turn on the flashlight and zoom to 8x to 10x.
- Tilt the phone so the light hits the surface at a shallow angle, around 20 to 30 degrees. The edges of each stamped character now throw a shadow.
- Rotate the device or the phone slowly. Some characters read better lit from the left, others from the right, so take two photos from different angles.
- On a polished surface, dim the flashlight: in LoupeLens, press and hold the flashlight button and slide down. Full brightness on brushed aluminum produces a white blob where the serial should be.
Without a phone flashlight, a desk lamp placed to one side works the same way: light from the side, look from above.
The characters that cause trouble
Most mistyped serials come down to a few look-alike pairs:
| Pair | How to tell |
|---|---|
| 0 and O | Many manufacturers do not use the letter O at all. A zero is often narrower, or has a slash or dot. |
| 1, I, and l | Many schemes skip the letter I. A 1 often has a flag at the top; a lowercase L is rare in serials. |
| 5 and S | The 5 has a flat top and a sharp corner; the S is curved throughout. |
| 8 and B | The B has a straight left side; the 8 is rounded on both sides. |
| 2 and Z | The 2 has a curved top; the Z is all straight lines. |
| Model vs serial | Model numbers repeat across every unit and often include letters like A, M, or a slash. Serials are unique and usually longer. |
When an entry form rejects what you typed, check these pairs on your photo first.
Special cases
IMEI on a phone
The IMEI is 15 digits and appears in tiny print on the SIM tray of many phones. Dialing *#06# shows it on screen, which is easier, but if the phone does not power on, look on the tray or the original box label. Magnify the tray at 10x with light from the side.
Rating plates on appliances
These are often inside a door frame at floor level. Use the rear camera with the flashlight on, hold the phone low so the lens faces the plate, and tap to take a photo. Then stand up and read the photo instead of lying on the floor. Take a second, wider shot that shows the plate and the appliance together, so you know which appliance the photo belongs to when you find it a year later.
Router labels
Photograph the router label before you mount it on a wall or slide it behind a cabinet. The default Wi-Fi password and admin address are on that label, and you will want them the next time the connection drops.
Keep a record
A clear photo of each label gives you a home inventory of serials for insurance, warranty claims, and support calls. Add a caption with the device name to each photo while you still remember which label belongs to what, and photograph the receipt next to the label so the purchase date is in the same place. When a product is sold or recycled, delete its photo so the list stays current. For tiny component markings, see electronics repair with a phone magnifier and reading labels on fuses, cables, and appliances.
Frequently asked questions
What is the difference between a serial number and a model number?
A model number identifies the product version and is the same on every unit of that model. A serial number identifies your individual unit and is different on every one. Warranty claims and stolen-property reports need the serial; buying parts usually needs the model.
How do I read a serial number to find the manufacture date?
Many manufacturers include a date code, often a year and a week or month, in the serial number, but the format varies by brand. Check the label for a separate MFG or date line first, then search the manufacturer’s support site for its serial number format or lookup tool.
Where is the serial number on a router?
On a label on the underside or back of the router, alongside the MAC address and usually the default Wi-Fi name and password. Photograph the label before mounting the router somewhere awkward so you can read it later without moving it.
How do I read a serial number stamped into metal?
Shine a light across the surface from a low angle so each stamped character casts a shadow, then view from above. With a phone, zoom to 8x to 10x, turn on the flashlight, and tilt the phone until the characters appear. Dim the flashlight on polished surfaces to avoid glare.
How do I find the IMEI of my phone?
Dial *#06# and the IMEI appears on screen. It is also in Settings under About, on the SIM tray in small print, and on the original box label. If the phone will not power on, magnify the SIM tray at about 10x with light from the side.
Is it a zero or the letter O in my serial number?
Many manufacturers leave the letters O and I out of serial numbers to avoid this confusion, so a round character is usually a zero and a vertical stroke is usually a one. Zoom into a photo of the label and compare the character's width with known digits nearby.