What does a tracking number look like?
A tracking number is a short uppercase string of letters and digits, usually 12 to 22 characters long, printed in plain text directly beneath the barcode on a shipping label. Five families cover almost every parcel a shopper receives: a 13-character international postal identifier built from two letters, nine digits and a two-letter country code; a 22-digit United States Postal Service string beginning 9400, 9205 or 9407; an 18-character UPS code beginning 1Z; a 12-digit FedEx number; and Canada Post numbers of 11, 13 or 16 characters.
The spaces printed between blocks exist for legibility and are not part of the number. Length and character mix identify the numbering scheme that issued the code, and nothing else about the shipment.
Who creates the number, and the moment it starts to exist
A tracking number is generated when the shipping label is produced, not when a carrier collects the parcel. The sender's shipping software, a warehouse label printer or a post office counter terminal draws the next serial from a block already allocated to that account, prints it under a barcode, and passes it to the buyer in a dispatch email.
Two allocation systems sit behind most consumer parcels. International postal items carry an identifier defined by Universal Postal Union standard S10, which fixes the string at 13 characters: a two-letter service indicator, an eight-digit serial number, one check digit and a two-letter country code. Domestic United States parcels carry an Intelligent Mail package barcode, which the mailer builds from its own mailer identifier and a serial number under Domestic Mail Manual 204.
The sequence matters for reading an empty result. Because the number is issued before the first physical scan, a freshly received code that returns no events is showing the normal state of a new label rather than a fault in the network.
Length and character mix, carrier by carrier
Eight documented formats account for the overwhelming majority of numbers printed on consumer parcels, and three properties tell them apart: total length, whether letters appear at all, and where the letters sit.
| Format | Length | Character pattern | Printed shape | Where it is used |
|---|---|---|---|---|
| UPU S10 international | 13 | 2 letters, 9 digits, 2 letters | RR 000 000 000 GB | Registered, insured and tracked letter post, parcel post and EMS between postal operators |
| USPS domestic | 22 | Digits only | 9400 1000 0000 0000 0000 00 | USPS Tracking, Priority Mail, Certified Mail, Signature Confirmation |
| UPS | 18 | 1Z, then 16 alphanumeric characters ending in a check digit | 1Z 000 000 00 0000 0000 | UPS domestic and international parcels |
| FedEx Express and Ground | 12 | Digits only | 0000 0000 0000 | The large majority of FedEx shipments, including FedEx Ground Economy master numbers |
| FedEx door tag | 14 | DT, then 12 digits | DT 000 000 000 000 | Left at the address after an unsuccessful delivery attempt |
| Canada Post counter and commercial labels | 11 or 13 | Alphanumeric, ending CA | AA 000 000 000 AA | Priority, Xpresspost, Expedited Parcel, Regular Parcel, Registered Mail, bills of lading |
| Canada Post online labels | 16 | Digits only | 0000 0000 0000 0000 | Labels bought through the Canada Post online shipping tools |
| Canada Post Priority Worldwide | 12 | Digits only | 0000 0000 0000 | Priority Worldwide receipt or waybill |
Canada Post publishes the plainest summary of a national numbering estate, and it shows how a single operator runs several schemes side by side.
"Tracking numbers are typically: 11 or 13 alphanumeric characters ending in CA or 16 digits." (Canada Post, Learn about tracking number formats, support knowledge base, accessed July 2026.)
The letters are the quickest discriminator in practice. Letters at both ends and nowhere in between is a postal S10 identifier. A string that opens 1Z and then runs alphanumeric is a UPS shipment number of 18 characters. Digits alone means a domestic scheme, separated by length: 12 for FedEx, 16 for a Canada Post online label, 22 for USPS.
Grouping and spacing, and why the printed form varies
The spaces inside a printed tracking number carry no data, so 9400 1000 0000 0000 0000 00 and the same 22 digits typed without a break resolve to the same item. Grouping is a typographic choice made by whichever system printed the label, and one consignment often appears with different spacing on the label, on the counter receipt and in the confirmation email.
Operators publish their own preferred grouping. Canada Post writes its 13-character form as two letters, three groups of three digits and two letters, and its 16-digit form as four groups of four. USPS domestic numbers are conventionally printed as five groups of four digits followed by a final pair. The 13-character international form is normally set the same way as the Canada Post alphanumeric one, because both descend from the same 2-9-2 pattern.
Two further properties hold across every format in the table above. All of them are uppercase, and none uses a hyphen, a slash, a full stop or any other punctuation mark as part of the number. A string containing a hyphen is rarely a parcel tracking number, and is far more often an order reference or a freight document number.
Where the number is printed on the parcel and its paperwork
A tracked parcel normally carries its number in four places: in human-readable text under or beside the barcode on the label, on the posting or drop-off receipt, in the dispatch email from the sender, and in the order record on the retailer's site. The label copy is the authoritative one, because it is the string the carrier's scanners resolve.
The human-readable line exists precisely so the number survives a damaged barcode. When a barcode will not scan, the characters printed underneath can be typed by hand, which is why a label carries the same value twice in two different encodings.
International postal items repeat the identifier across the dispatch paperwork as well. The same 13 characters appear on the item label and on the customs declaration attached to it, so a posting receipt kept after the parcel has gone still carries the string needed to open an inquiry. Retailers that use a fulfilment partner often expose the number only after the parcel is handed over, which is the most common reason an order page shows no tracking on the day of purchase.
What the barcode holds that the printed number does not
The barcode on a parcel label is a data string rather than a picture of the printed number, and on a USPS domestic label it carries routing and service elements the human-readable number leaves out. Scanning that barcode with a consumer barcode app can therefore return a longer run of digits than the number printed underneath it.
The Intelligent Mail package barcode uses "a variable-length format that is determined by the elements selected by the mailer, and supplies tracking and routing data for packages and extra service applications." (United States Postal Service, Domestic Mail Manual 204, section 2, accessed July 2026.)
The encoding generally follows the GS1-128 specification, and application identifier 420 introduces the domestic postal routing element that encodes the destination code. Those elements address sorting machinery rather than customers, and the portion meant to be typed into a tracking form is the number printed in plain text on the label.
The practical consequence is a false alarm avoided. A scanner app that returns 26 or 34 characters has read the full data string, not a longer tracking number, and the value to search with is the printed one that matches a documented length of 12, 13, 16, 18 or 22.
The other numbers on the same label, and how to rule them out
A commercial parcel label routinely carries five or more distinct numbers, and only one of them resolves on a carrier tracking page. Eliminating the other four is usually faster than guessing at the carrier.
| Number on the parcel | Who assigns it | How to recognise it |
|---|---|---|
| Order number or order ID | The seller, at checkout | Typically 6 to 12 characters, frequently carrying a hyphen or a store prefix, and issued before any carrier is involved |
| Shipper or customer reference | The sender's own system | A purchase order, invoice, part number, returns authorisation or bill of lading value, searchable only alongside the account that created it |
| Door tag number | The delivery driver, after a failed attempt | DT followed by 12 digits, tied to the attempt rather than to the consignment record |
| Postal routing element | The carrier's sortation system | Sits inside the barcode data string behind application identifier 420 and encodes a destination code, not an item identity |
| Customs form number | The Universal Postal Union form series | CN 22 and CN 23 name declaration forms; neither is an item number |
| Service, zone and weight blocks | The label software | Very short codes, often 1 to 4 characters, printed in the corners of the label |
Carriers treat most of these as separate search types rather than as tracking numbers. FedEx documents the door tag case explicitly.
"Door tag numbers start with the letter's 'DT' followed by 12 numbers." (FedEx, Track API documentation, FedEx Developer Portal, accessed July 2026.)
The same documentation lists purchase order number, customer reference, invoice, bill of lading and part number as reference searches distinct from tracking by number. The nearest neighbour, and the one that costs shoppers the most time, is the order identifier: the difference between an order number and a tracking number is that the shop issues one and the carrier issues the other.
Marketplace orders, where the number arrives late and changes shape
A cross-border marketplace order commonly produces two numbers in sequence: an internal order identifier at checkout, then a 13-character postal identifier once the consolidator hands the parcel to a postal operator. The second one is the trackable value, and it typically appears days after the purchase rather than at the moment of payment.
The shape of that second number follows the postal product the consolidator bought, not the storefront that sold the goods. Consecutive orders from one seller can arrive under different two-letter prefixes and still travel the same route, and the final two letters name the country under whose authority the identifier was issued.
A second identifier can also appear at the destination. Where the receiving operator applies its own domestic barcode on arrival, the parcel ends up carrying two strings of different lengths, and searching the origin number and the destination number can return two partial timelines for one item. That is an artefact of the handover between networks, not evidence that the consignment was split in two.
What the shape of a number cannot tell you
Length and character mix identify the numbering scheme, and they carry no information about destination, service speed or the company that will make the final delivery. A 12-digit number and a 22-digit number can describe parcels arriving at the same address on the same morning.
Three limits are worth stating plainly. The number does not change as the parcel moves, so the same 18 characters read identically on day 1 and on day 30. The number does not encode weight, declared value or contents. And the operator that issued the number is not necessarily the one that hands the item over, because postal operators and integrators subcontract final delivery to partners.
Nor is a number permanent. Under standard S10 an international postal identifier may not be reused within 12 calendar months, and a gap of 24 months or longer is recommended, so a code kept from a delivery two years earlier can eventually resolve to a different consignment. Reading the movement of a parcel means reading the scan history instead, starting with what in transit means on a timeline.
What to check when a number matches no known format
The first test is arithmetic: count the characters and compare the total against 12, 13, 14, 16, 18 and 22. A string whose length matches none of those is usually not a carrier tracking number at all.
The string is 6 to 12 characters and contains a hyphen or a store name. That is an order identifier from the seller. The tracking number is issued later, when the label is printed, and normally arrives in a separate dispatch message.
The string is 13 characters but the two opening letters look unfamiliar. The format is valid. Only the first character is standardised across operators and the second is a national allocation, so unfamiliar pairs are common and legitimate.
The string is the right length and returns no events. The label has been created but not yet scanned. Numbers exist from the moment of label generation, so a gap between issue and first scan is expected rather than exceptional.
The parcel carries two barcodes of different lengths. One is the original identifier and one was applied by a handler further along the chain. Search both, and read a longer digit-only string as a domestic scheme rather than an international one.
The string mixes upper and lower case or contains punctuation. No consumer parcel format documented above uses lower case or punctuation, so the value has almost certainly been copied out of a reference field rather than off the label.
When the shape is confirmed and the number still resolves nowhere, the sender is the party that can name the carrier, because the sender's account issued the label. The wider anatomy of the string, and how the elements inside it are assembled, is covered in the guide to the logistics tracking number.