Shipping labels that scan at every hub

A parcel is scanned many times before it reaches the customer: at pickup, when it enters the first hub, at the sort, when it is bagged, at the delivery centre and at the door. A shipping label is the parcel's boarding pass. It is checked at every gate.

When a scan fails, the parcel waits for a person.

That person types the tracking number by hand, or sets the parcel aside to deal with later. Both cost time, and typing by hand is where wrong digits creep in. One wrong digit can send a parcel meant for Pune towards Patna.

The good part is that most of what makes a label readable is in our hands as senders. Let us go through the standard step by step, and then the common mistakes.

My short answer: print a 4 x 6 inch self-adhesive label at 100% scale, with dark solid bars and clean margins. Stick it flat on the largest face of the parcel, away from seams, edges and tape. Remove every old label. Keep the label dry and out of the sun until pickup.

How a hub reads your label

There are two kinds of scanning on a parcel's route. Some scans are done by people with handheld scanners or phones, usually at pickup, at small hubs and at delivery. Larger hubs move parcels on belts past fixed scanners or cameras that try to find the barcode on whatever face they can see.

I find it helps to picture the label from the scanner's side: a quick look, in uneven light, at a box that may be lying on any face.

Both kinds of scan need the same three things. The bars must be dark and sharp, the white margins around them must be clear, and the label must be flat and facing outward. A label folded over an edge, hidden under a strap, or on the bottom of the parcel makes every one of those scans harder.

Size: 4 x 6 inch

Most courier software prints labels in two formats: a single 4 x 6 inch label for thermal printers, or four labels on one A4 sheet for office printers.

I prefer the 4 x 6 inch self-adhesive label. GS1, the barcode standards body, names A6 (105 x 148 mm) or 4 x 6 inch as its compact size in the GS1 Logistic Label Guideline (Release 1.3, July 2019). Desktop thermal label printers are commonly 4 inch wide, so the size suits them.

One warning here. Do not take a marketplace label made for A4 and shrink it onto a 4 x 6 label with "fit to page". Shrinking makes the narrow bars and the margins smaller than the courier's software planned. Choose the thermal or 4 x 6 format in the panel, and print at 100%.

Placement: where the label goes

1. Put it on the largest flat face of the parcel, usually the top.
2. Keep it off seams, edges, flap closures and sealing tape. The UPS Packaging Guidelines (November 2024) say exactly this, and the reason is simple: the label tears or lifts when the box flexes.
3. Never wrap it around a corner. A barcode bent across two faces is hard to read from either side.
4. On polybags and mailers, stretch the area flat before you stick the label. Keep it away from the seal and the flap. GS1 lists wrinkling during application as a common problem.
5. Print one label, stick it, then print the next. The GS1 guideline suggests printing labels one at a time to cut the risk of a label going on the wrong parcel.

If I had to train a new packer on only one of these, I would pick the second, because a label on a seam is a label that tears.

Quiet zones: the white margins that matter

The quiet zone is the blank space on each side of a barcode. The scanner uses it to find where the code starts and stops. For GS1-128 barcodes on logistic labels, GS1 asks for a quiet zone of at least 10 times the width of the narrowest bar on each side.

Courier software normally sets this space correctly. We lose it on the packing table, in four common ways.

1. The printer is not calibrated, so the print drifts towards the label edge.
2. Tape or a "Fragile" sticker is laid across the end of the barcode.
3. Someone writes on the label next to the bars.
4. The label is trimmed with scissors to fit a small parcel.

Protect the label until pickup

Most courier labels from label printers are direct thermal. The image is made by a heat-sensitive coating, with no ink. That coating reacts to heat, sunlight, water, oil and rubbing.

The GS1 guideline does not consider heat-sensitive thermal paper acceptable on pallet and carton labels, for exactly this reason. Courier labels get away with it because they live for only a few days. So make those few days easy for the label.

1. Keep labelled parcels out of direct sun and away from hot walls and roof sheets while they wait for pickup.
2. In the monsoon, keep parcels dry. If a parcel may get wet, use a clear self-adhesive pouch, or clear tape laid flat over the whole label.
3. Do not stack wet or oily goods on labelled parcels.

I would also store the label rolls themselves in a cool cupboard, and not on a shelf above the packing table where the afternoon sun falls. A roll can be damaged by heat before a single label is printed.

If you are choosing labels for anything that must last longer than a courier trip, read our lesson on direct thermal or thermal transfer.

Old labels: remove them or cover them fully

A reused carton can carry an old courier label, an old barcode and a supplier's carton marks. A scanner does not know which code is the live one. The GS1 guideline warns that extra labels repeating the same kind of data risk non-scans and confusion.

So peel old labels off. If they will not come off, cover each one completely with a plain opaque label. A pen line through an old barcode is not enough, because the scanner may still find enough bars to read.

Check every face of the box, including the bottom and the sides.

Printer settings for crisp barcodes

1. Set the label size to 4 x 6 inch in the printer driver. A 203 dpi printer, which prints 8 dots per mm, is fine for courier labels.
2. Set the darkness to the lowest setting that gives solid bars and clean gaps. Zebra's ZT211 guide shows the problem with too much darkness: bars grow, small text fills in, and barcodes printed sideways suffer first. Too little darkness leaves broken bars.
3. If you raise the print speed, check the darkness again. The Zebra white paper Selecting the Right Label (2023) notes that faster printing needs more darkness to keep barcode grades up.
4. Calibrate the printer whenever you load a new type of label roll, so the print sits square on the label.
5. Clean the printhead. Zebra's ZT111 cleaning schedule asks for it after every roll in direct thermal mode, using 99.7% isopropyl alcohol. Your model's manual may say otherwise, so follow it.
6. Watch for a thin white line running down every label. It usually means dirt or a damaged dot on the printhead. Clean first. If the line stays, the head needs service.

My advice is to write these settings on a card and tape it to the printer. On a busy sale day, somebody will otherwise turn the darkness up "to be safe".

A two-minute check each morning

We should do this before the first pickup, not after the first complaint.

1. Print the first label of the day and scan it with a handheld scanner or a phone. It should read first time.
2. Look at it closely: solid bars, clean white gaps, full margins on both sides, sharp small text.
3. Check the background. A grey or yellow tint usually means the rolls have seen heat, so move them somewhere cooler.
4. Look at the last parcel packed: one label, flat on the top, off the tape, no old codes showing.

I cannot promise that every hub will read every parcel. Scanners, lighting and handling differ from one hub to the next, and we do not control any of them. What we can control is the label, so let us get that part right.

Labels are made by Jagannath Labels, our group's label company. If your parcels keep coming up as no-reads, send us a photo of a printed label next to a ruler and your printer model through the contact page. We will tell you what we would change first. If labels are lifting off polybags or cartons, our lesson on label adhesives covers that side of the problem.