Tracking looks like a live map. It is not. It is a chain of discrete records, each created when a parcel is physically handled, stitched together from networks with no common format. Understanding what creates each record, and what happens in the silence between them, answers almost every tracking question a shopper, a merchant or an engineer asks.
What a tracking event actually is
A tracking event, often called a scan, is a record written at the moment something happens to a parcel. A barcode is read at a depot. A sortation machine registers an item. A driver taps "delivered" on a handheld. A customs system posts an outcome.
Every event carries roughly the same four things:
- an identifier that ties the event to one specific item
- a status or event code describing what happened
- a timestamp
- a location, at whatever level of precision the operator chooses to publish
That is the whole of it. There is no continuous signal, no GPS beacon in the box, no telemetry between events. If nothing handles the parcel, nothing is recorded.
Why gaps happen
Most tracking anxiety comes from silence, and silence usually has a mundane cause:
- Nothing happened. A parcel on a long overnight run generates no events, because no one touched it.
- The parcel changed hands. Handovers between an origin carrier, an airline and a destination carrier are the most common place for a visible pause.
- Data is batched. Some operators publish in scheduled uploads rather than in real time, so the event exists before you can see it.
- The final leg is subcontracted. If the last-mile partner does not report back to the originating network, the trail thins out near the end.
Worth knowing: a gap in tracking is a gap in reporting, not usually a gap in movement. The two feel identical to a customer, which is why how a merchant communicates during a quiet period matters more than the quiet period itself.
The journey, from label to doorstep
The lifecycle is the same almost everywhere, even when the wording differs.
- Label creation. The sender generates a shipping label and, with it, a tracking number. The number now exists in the carrier's system, but the parcel does not exist in the physical network yet. This is what "Info Received", "Label Created" or "Pre-Shipment" means.
- First scan, or acceptance. The carrier physically takes custody: a pickup, a counter transaction, a drop-off scan. This is the first event proving a real parcel exists.
- Linehaul. The parcel moves between facilities by road, rail or air, producing arrival and departure events with long quiet stretches between them. Cross-border items are consolidated into larger units, so an individual item can be invisible while its container moves.
- Customs, for cross-border items. Clearance is a data process first and a physical process second. More on this below.
- Final mile. The parcel reaches the delivery depot, is sorted to a round and goes out with a driver, ending as a delivery, a safe place, a neighbour, a pickup point or a failed attempt.
Why the shape of this matters commercially
Narvar's State of Post-Purchase 2025 research, based on 3,461 US online shoppers surveyed in August 2025, found that 74% had experienced a late delivery in the past year and 86% hit at least one delivery issue. It also found that 73% say a visible estimated delivery date influences their purchase decision, 40% will not buy at all if no delivery date is shown, and 38% say frequent tracking updates reduce their anxiety. Age matters: 60% of 18 to 29 year olds would not repurchase after a late delivery, against 17% of over-60s. This is vendor-run research with disclosed methodology rather than independent study, but the direction matches what most merchants see in their own support queues.
The practical reading: the delivery promise sells the order, and the tracking experience decides whether the customer comes back.
How postal networks exchange tracking data
Here the picture gets more precise, because the postal world has a standards body. The Universal Postal Union maintains two families: Technical Standards, prefixed S, and EDI Messaging Standards, prefixed M. The catalogue was updated on 27 February 2026.
| Standard | Family | What it does |
|---|---|---|
| S10 | Technical | The 13-character international item identifier |
| S34 | Technical | IMPC codes, identifying International Mail Processing Centres |
| M40 (EMSEVT V3.0) | EDI messaging | Item-level tracking events |
| M33 (ITMATT V1), M52 (ITMATT V2) | EDI messaging | Item attributes and customs declaration data |
| M43, M55 (CUSITM) | EDI messaging | Item data sent to customs |
| M44, M56 (CUSRSP) | EDI messaging | The customs response back to the operator |
| M42 (eVN) | EDI messaging | Electronic verification notes |
| M48 (CARDIT V2.1) | EDI messaging | Carrier documents international transport advice; consignment data sent from the origin postal operator to the transport provider |
| M30 | EDI messaging | EDI exchange between postal handling organisations |
| M85 | EDI messaging | The data dictionary underpinning the M-series |
S10, the identifier you have already seen
S10 defines a fixed 13-character structure: a two-letter service indicator, an eight-digit serial number, a check digit, and a two-letter ISO country code associated with the UPU member country under whose authority the identifier is issued. The UPU publishes a check-digit validator for it.
For a developer, a syntactically valid S10 number reveals the issuing-country code and the broad service class before you have called anything. The suffix is an identifier-allocation field, so it should not be treated as standalone proof of where a parcel was physically posted. It also does not tell you whether the item exists, or which operator will handle the final mile.
EMSEVT, the event message
M40, better known as EMSEVT and currently at version 3.0, is the message that carries item-level tracking events between operators. It is the reason a shopper in one country can see an event generated by a sorting centre in another. The reference documentation is published by EMS and is worth reading if you are mapping event codes.
S34 matters more than it sounds: because facility identifiers are standardised as IMPC codes, an event location resolves to a known processing centre rather than a free-text string that varies by operator.
Why customs data moves ahead of the parcel
Electronic advance data is the part of the chain that most often explains an unexplained delay.
ITMATT, carried by M33 and M52, is the electronic equivalent of the CN22 or CN23 customs declaration. It is exchanged from the origin operator to the destination operator ahead of the parcel's arrival, and the joint WCO-UPU guidelines say it should ideally be generated at the EMA "posting or lodging" tracking event. The declaration data leaves as the item is accepted, so the destination has it long before the aircraft lands.
Worth knowing: the UPU does not mandate electronic advance data. National and regional law does. The US STOP Act requires it for all packets. The EU's ICS2 requires it for all incoming goods, and it must be in place before the goods are handed over to the air carrier. From 1 September 2025, six-digit WCO HS tariff codes became mandatory for commercial items where the destination requires them.
For merchants, this turns product data into a shipping dependency. Vague descriptions, missing or incorrect HS codes and inaccurate declared values are the reason a parcel sits at a border showing "Held at Customs" and no further detail. The fix is upstream, in the catalogue, not downstream in customer support.
Why tracking is fragmented, and what aggregation involves
This is the strategic point, and it is simple to state: the UPU standards above govern the postal network only.
UPS, FedEx, DHL and Amazon each use proprietary event code sets. There is no cross-carrier standard, and as of 2026 none is emerging. Two parcels moving between the same two cities on the same day can produce entirely different vocabularies, granularity and notions of what counts as an event.
The market is moving away from the standardised end, not towards it. Pitney Bowes' Parcel Shipping Index 2026, now a US-only report, puts 2025 US volume at 23.1 billion parcels, up 3.3% from 22.4 billion in 2024, with revenue per parcel of $9.34, up 2.9%. That is 732 parcels per second and 63.3 million per day, with a forecast of 31 billion by 2031. Within that:
- Amazon Logistics overtook USPS as the largest US carrier by volume, at 6.9 billion parcels against USPS at 6.2 billion
- USPS volume fell 8.8%, and UPS fell 8.7% to 4.3 billion, while FedEx grew 5.1% to 3.9 billion
- Alternative carriers, including OnTrac, GLS, Veho, UniUni and SpeedX, grew 127% to 1.8 billion parcels, with revenue share doubling from 3.4% to 7.2%, driven largely by Shein and Temu volume
Pitney Bowes explicitly names delivery tracking and reliability as the weak point of that alternative segment. The fastest-expanding slice of the market is also the slice with the least dependable tracking data, and none of it is bound by UPU conventions.
One caveat on scope: this index is now US-only. The last global edition was the 2023 report covering 2022 data, so any current worldwide parcel figure deserves caution.
What aggregation actually has to do
This is why tracking aggregators exist, and why the work is less trivial than it looks. A platform such as Ship24, which integrates over 2,500 couriers and 3PLs, has to handle at least the following:
- Carrier detection. Infer the likely carrier from an identifier alone, covering S10 patterns and proprietary formats.
- Multi-leg resolution. Follow an item across an origin carrier, a linehaul partner and a final-mile carrier, often under different numbers.
- Ingestion strategy. Reconcile polling against push, since some sources expose APIs, some webhooks and some neither.
- Code normalisation. Map hundreds of proprietary event vocabularies onto one status set without destroying the original detail.
- Deduplication and ordering. Remove repeats, resolve timezone inconsistencies, and produce a coherent chronological timeline.
- Location normalisation. Turn IMPC codes, depot names and free text into something a customer can read.
None of that is exotic engineering. All of it is unavoidable if you want one timeline per order.
What "good" tracking data looks like
The most useful external benchmark available is Google's package tracking specification, last updated on 14 July 2026. It defines what Google requires of a carrier API, and is a reasonable proxy for "good enough for a consumer-facing experience".
On performance, it requires carrier APIs to respond in an average of 700ms or less, with a 95th percentile of 1,000ms or less. That is a demanding bar for any integration built on nightly batch files. On content, the requirements are short and revealing:
| Field | Status | What it signals |
|---|---|---|
CurrentStatus |
Mandatory | The single most important field. If you can only publish one thing, publish this |
PromisedDate |
Recommended | The delivery promise, which shoppers weigh heavily |
TransitEvents |
Recommended | The event history that makes a timeline possible |
TrackingURL |
Recommended | A route back to the authoritative source |
CanReschedule |
Recommended | Whether the customer has any agency over the outcome |
Equally instructive is what the specification refuses: it explicitly rejects any personal or geographic data about the sender or the recipient. Good tracking data is item-centric, not person-centric. Google's Package Tracking Early Adopters Program is also closed to new partners, so treat this as a benchmark to design against, not a channel to plan around.
A practical checklist. Assessing your own tracking quality: is there always a current status; is it fresh within minutes rather than hours; does the timeline survive a carrier handover; does the location text mean anything to a customer; and does the customer have a next action when something goes wrong.
Where this leaves you
Parcel tracking is a chain of handling records, exchanged over standards that cover only part of the network, in a market whose fastest-growing carriers are the least standardised of all. Nothing about that resolves itself: no cross-carrier standard is emerging, volume keeps rising, and the carrier mix keeps fragmenting.
What is within reach is the layer on top. Status normalisation, fresh data, a timeline that survives handovers and honest communication during quiet periods are all achievable today, and they are what customers actually experience. The standards explain the plumbing. The presentation decides whether anyone trusts it.
Sources & methodology
- Universal Postal Union (UPU) Standards programme and catalogue Primary source.
- World Customs Organization and UPU Joint WCO–UPU guidelines on postal customs data Primary source.
- Google Search Central Package tracking specification Primary documentation.
- Universal Postal Union (UPU) Catalogue of UPU Standards Primary source.
- Pitney Bowes Parcel Shipping Index 2026 Company research.
- Narvar State of Post-Purchase 2025 Company research.
