Tracking by container number means looking up the 11-character number written according to ISO 6346 (for example CSQU3054383) on the carrying shipping line's website or on a tracking platform. The results screen lists the container's terminal gate-in, loading onto the vessel, transshipment and discharge at the port of destination, with dates and ports, and also shows the next planned step.
How do you read a container number?
Every sea container carries the same identification number on its doors and side walls. The format is defined by the ISO 6346 standard; the register of owner codes is kept by the Paris-based BIC (Bureau International des Containers). The number has four parts:
| Part | Example: CSQU3054383 | Meaning |
|---|---|---|
| Owner code | CSQ | Three letters identifying the owner or operator of the container |
| Equipment category | U | U: freight container, J: detachable equipment related to the container, Z: trailer and chassis |
| Serial number | 305438 | Six-digit number assigned by the owner |
| Check digit | 3 | A single digit that verifies the number has been written correctly |
Below the identification number there is usually a four-character size-type code such as 22G1 or 45G1. The first character shows the length (2: 20 ft, 4: 40 ft), the second the height (2: 8'6", 5: 9'6" high cube), and the last two the type; G1 is a general-purpose dry cargo container.
How is the check digit calculated?
- Letters are given numerical values: starting with A=10 and skipping multiples of 11 (B=12, C=13 … Z=38).
- Each of the first ten characters is multiplied by 1, 2, 4, 8 … 512 according to its position.
- The products are added up and divided by 11; the remainder is the check digit. If the remainder is 10, the digit is taken as 0.
For CSQU305438 the total is 6185; divided by 11 the remainder is 3, so the full number is CSQU3054383. If the shipping line's website returns no result, this calculation is the first thing to do: mixing up the letter O and the digit 0, or I and 1, is the most common query error.
How do you track step by step?
- Identify the line: The owner code often points to the shipping line. However, for containers owned by leasing companies and for SOC containers the code does not reveal the line; find the right line from the bill of lading or the booking document.
- Run the query: Enter the container number without spaces in the tracking field on the line's website. Most lines also allow searching by bill of lading and booking number on the same screen.
- Read the events: The location and date of the latest event are assessed together with the next planned port and the estimated time of arrival.
- Automate notifications: Companies working with several lines bring events together on a single screen through e-mail notifications, a multi-carrier tracking platform or an API.
What do the event records tell you?
| Event | When does it occur? | Why does it matter? |
|---|---|---|
| Empty gate-out | The empty container leaves the depot for loading | The container number is assigned to the booking at this moment |
| Gate-in (full) | The loaded container enters the terminal | It is proof of delivery before the cut-off |
| Loaded / Vessel departure | It is loaded onto the vessel and the vessel sails | It shows the container is on the planned vessel |
| Transshipment | It is discharged at the transshipment port and loaded onto another vessel | This is the stage where delays occur most often |
| Discharged | It is discharged from the vessel at the port of destination | Free time usually starts running from this date |
| Gate-out (full) / Empty return | It leaves for the consignee and is returned empty | It determines the demurrage and detention calculation |
So that lines publish these events in a common language, the DCSA Track & Trace standard groups them into shipment, transport and equipment events.
Container number or bill of lading number?
The container number tracks the physical box; the bill of lading number tracks a shipment and all the containers in it. For an FCL shipment of five containers, a single bill of lading query shows all five at once. Groupage (LCL) cargo is different: the container belongs to the consolidator and also holds other cargo. In that case it is more accurate to follow your cargo through the house bill of lading issued by the consolidator; the difference between the two documents is explained in the master and house B/L entry.
The shipping line's website is event-based, which means no new record appears while the vessel is at sea. For the vessel's current position, AIS vessel tracking is used; the container's road leg after the port is followed through vehicle tracking based on location from the driver app.