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Container Tracking Number Format: API Examples by Shipping Carrier
If you work in logistics, the entire supply chain often depends on a single piece of data, the container number. For freight forwarders, shippers, and developers building Transportation Management Systems (TMS), this 11-character sequence is the only thing standing between visibility and total darkness.
To the untrained eye, these numbers look like a random scramble of letters and numbers. They aren’t. Every character follows the strict ISO 6346 standard. To create accurate tracking tools or manage shipments effectively, you must understand how these IDs work.
Our guide breaks down the code’s anatomy, explains why tracking matters, and provides specific container tracking number examples to help you decode the variety of prefixes used by major shipping lines.
What is Container Tracking and Why is it Important?
Container tracking is the process of monitoring a shipping unit’s location and status from the port of loading to the final destination. It has evolved from a manual task of checking websites and making calls into a digital necessity driven by API integration.
Accurate tracking is critical for three main reasons:
Mitigating Fees: Real-time visibility helps you avoid massive demurrage and detention charges by alerting you exactly when a container is ready for pickup.
Managing Disruption: If a container gets “rolled” or delayed, early data allows you to reschedule trucks and warehouse slots proactively.
Customer Expectations: B2B clients now expect “Amazon-style” visibility. Automated updates reduce support emails and build trust.
The Anatomy of an ISO 6346 Container Number
A standardized maritime container number consists of 11 characters divided into four distinct sections.
1. The Owner Code (Prefix) The first four characters are always letters. This “Owner Code” identifies who owns or operates the container and is registered with the Bureau International des Containers (BIC). For example, “MSKU” belongs to Maersk.
2. The Equipment Identifier The fifth character is a single letter. You will almost always see U (freight container), though J (detachable equipment) and Z (chassis) exist.
3. The Serial Number The next six characters are numbers. This is the unique ID assigned to the box by the owner.
4. The Check Digit The final character is the Check Digit. It is the result of a mathematical algorithm (Modulo 11) based on the previous 10 characters. It acts as a built-in “spellcheck” to validate the number immediately.
Carrier-Specific Container Tracking Number Examples
One of the biggest sources of confusion is the sheer number of prefixes. Major shipping lines often operate under multiple codes due to historical mergers. Here are the specific prefixes you will encounter for the world’s major lines:
Maersk Line: The most common prefix is MSKU (e.g., MSKU 907103 4). However, due to past acquisitions, you will also see MAEU, MGLU, MRKU, and even the legacy P&O Nedlloyd code PONU.
MSC: The standard is MSCU (e.g., MSCU 682541 9), but they also utilize MEDU and MCLU.
CMA CGM: While CMAU (e.g., CMAU 190280 2) is standard, their fleet includes codes from acquired companies like APL (APLU) and ANL (ANNU).
COSCO: Their primary identifier is COSU (e.g., COSU 713009 6). Following mergers, it is also common to see CSNU and CBHU.
Hapag-Lloyd: They primarily use HLCU (e.g., HLCU 372115 1). You may also track containers starting with UACU from their merger with UASC.
ONE (Ocean Network Express): Their new containers use ONEU (e.g., ONEU 540916 0), but you will still see legacy prefixes from the three Japanese lines that formed the company: NYKU, MOLU, and KKFU.
Evergreen: Common codes include EGLV, EISU, and EMCU.
Common Challenges in Container Tracking:
Why Do Leasing Prefixes Create Blind Spots?
The carrier moving the box isn’t always the owner. A huge portion of global trade moves in containers owned by leasing companies (e.g., Triton or Textainer) rather than shipping lines. You might see a container with the prefix TRHU. That box could be on a Maersk ship today and a CMA CGM ship tomorrow. If your software relies solely on prefixes to identify the carrier, these leasing codes will break your logic.
In addition, trying to manually validate numbers, decode leasing prefixes, and standardize different carrier formats is a drain on resources.
This is why we built the JSONCargo Container Tracking API. We aggregate data from over 95% of global carriers, including NVOCCs and leasing companies. We manage validation and carrier identification in the background. You just send the number, and we return a clean, standardized JSON API response. This allows you to stop worrying about prefixes and start focusing on your logistics operations.