What are electronic shelf labels and how do they work?

An electronic shelf label (ESL) is a small battery-powered display fixed to the shelf edge that shows a product’s price. It does not decide that price: it receives it by radio from a gateway connected to central software, which takes it from the store’s ERP or pricing system.

The short version

• An ESL is only the last link in a chain: source data, software, gateway and label.
• The display is usually e-paper: it holds its image without power and only draws battery when the content changes.
• Communication is by radio; the label has no cable and does not join the store’s wifi.
• It is neither RFID nor anti-theft, although all three can sit side by side in one store.
• What shapes the outcome most is not the screen but the quality of the pricing data that goes in at the start.

The four components of an ESL system

When people say “digital price tags” they usually mean the display, because that is the part you can see. A complete system has four pieces, and any one of them can be the reason a price does not change.

Component	What it is	What it does	Where it tends to fail
Data source	ERP, pricing system, POS or PIM	The single source of truth for price, product name and attributes	Wrong price loaded, duplicate barcode, empty fields
Management software	Central application, cloud or on-premises	Links each product to its label, builds the screen image and schedules updates	Stale links, half-finished ERP integration
Gateway (access point)	Radio device connected to the network	Translates between the store network and the labels’ radio	Insufficient coverage, power, congestion
Label	Display, microcontroller, radio and battery	Receives the content, draws it and confirms	Flat battery, poor position relative to the gateway

1. The data source

The label holds no pricing logic. The company’s own system does: an ERP, a price-list module or the store management software. The label software connects to it (usually through an API, a file exchanged at intervals or a POS integration) and takes the price, the description and, as the case may be, the unit price or the current promotion.

This has a practical consequence worth understanding before you buy: if the source data is wrong, the label will show it wrong, and it will show it fast. ESLs speed up how a change spreads, not how it is checked.

2. The management software

This is the operational brain. It keeps the table that matches each product code to the unique identifier of one or more physical labels. When a change comes in, it decides which labels have to be redrawn, generates the image or the set of fields each one will show according to its template and size, and queues the transmission. It also stores the state of every label: last time it responded, battery level and whether the image on screen matches the expected one.

A lot of what you notice day to day is decided here: what happens to a product with no label assigned, how a new label is linked (scanning with a handheld, with a phone or with NFC, depending on the vendor) and who is allowed to change templates. Those details are covered in the implementation guide.

3. The gateway

A label does not talk to the ERP. It talks to a gateway, and the gateway talks to the software. It bridges two worlds: an ordinary network connection (cable or wifi) on one side, and the low-power radio the labels use on the other. A store needs several, spread out to cover the aisles; how many depends on the layout, the shelving material and the manufacturer. For what to look at when sizing them, see the article on the electronic shelf label gateway.

4. The label

Inside, a label has four things: a display, a microcontroller, a radio module and a battery. The display is usually e-paper, although LCD models exist; the comparison is in LCD versus e-paper and the full set of display, radio and size options in the technology guide.

The microcontroller spends most of its life asleep. The label wakes at intervals, listens for anything addressed to it and goes back to sleep. That cycle is what lets a battery last for years, and it is also why a price change is not instantaneous to the millisecond: it depends on when the next listening slot falls. What else affects battery life is discussed in the article on ESL batteries.

How they work: one price change, step by step

This is the journey of a single change, for example a price cut scheduled for store opening.

 ┌────────────┐   ┌───────────────┐   ┌────────────┐  radio  ┌────────────┐
 │ ERP / POS  │──▶│ ESL software  │──▶│  Gateway   │ ~ ~ ~ ~▶│   Label    │
 │ (price)    │   │ (linking,     │   │ (network ⇄ │ ◀~ ~ ~ ~│ (display,  │
 │            │   │ image, queue) │   │  radio)    │ confirms│  battery)  │
 └────────────┘   └───────────────┘   └────────────┘         └────────────┘
   source data         brain          network/radio bridge      last link
   ◀──────── regular network (cable, wifi) ───────▶  ◀── low-power radio ──▶

1. The price changes in the source system. Someone edits it, or a scheduled rule does. No label has been involved so far.
2. The software detects the change. It receives it through the integration or reads it at the next synchronisation. It compares it with what it believes each label is showing and flags the ones that are out of date.
3. It works out which labels are affected. A product can have one label, several (in different shelf positions) or none. The software knows this relationship because it was created when the labels were linked.
4. It generates the content. It applies the template for each size and composes what the customer will see: price, description, unit price, promotion and a barcode where needed.
5. It hands it to the right gateway. The message travels across the store network to the gateway that covers that area.
6. The gateway broadcasts it by radio. With the Bluetooth standard, for example, the gateway sends out a periodic sequence of advertisements in time slots, and each label synchronised to that sequence knows when to listen and when to answer.
7. The label receives it and redraws. It checks that the message is meant for it, updates its memory and refreshes the screen. This is the only step where e-paper uses a noticeable amount of energy.
8. The label confirms. It sends back an acknowledgement. The software marks the change as applied, or retries if no reply arrives.

Steps 6 and 8 carry an important nuance. In the Bluetooth profile for shelf labels the link is two-way: the technology that makes it possible (Periodic Advertising with Responses, introduced with Bluetooth 5.4) adds to periodic broadcasting the ability for the receiver to answer in its own slot. According to the Silicon Labs documentation, labels are organised into groups (up to 255 per group, of which only 23 can answer in the same slot window), and the interval between advertisements is a trade-off: shorter means lower latency but more battery use. Vendors with their own radio, rather than Bluetooth, solve the same problem with their own protocols; the principle (listen at intervals, answer in turn) is similar.

How long the whole journey takes depends on how many labels are affected, how busy the gateway is and the listening interval. The figures vendors quote are marketing until they are measured in a real store, which is why it pays to measure them in a pilot before signing. If the journey fails at any step, the symptom is always the same (the label price does not match), and finding the step where it happens is exactly what the article on labels that are not updating explains.

What the customer sees and what staff see

With e-paper, the image stays on screen even if the label receives nothing. If a gateway goes down, the customer still sees the last price received. That is an advantage (no blank screens) and a risk (a disconnected label does not announce on its own that it is out of date). That is why the software includes a status dashboard: it is the only way to know which labels have not responded for days.

What an ESL is not

The most common confusion, and the one behind wrong explanations on vendors’ commercial pages, is mixing up the price label with other in-store technologies that are also called tags and also use radio.

It is not RFID

RFID is an identification technology. A reader sends a signal; a tag, which may have no battery, answers with a number that identifies an object. It is used to locate and count things, even without seeing them and without them being in plain view. An RFID tag has no display and shows nothing to the customer.

An ESL does the opposite: it identifies no goods, it shows information it receives. It is a display with a radio, not a transponder. It does not know what product sits next to it; the software does, because it linked the two. That is why a store with ESLs does not need RFID, nor the other way round, and why you cannot get an RFID-style inventory from price labels.

There are two places where the two get mixed without being the same thing. One is linking: some systems use NFC (a short-range variant of the RFID family) to pair a label with a product by tapping a phone on it, but that is the enrolment method, not how the price is transmitted. The other is the vendors’ offer, which may bundle price labels, RFID readers and sensors on one commercial platform. Being sold together does not make them the same thing.

It is not anti-theft

Electronic article surveillance (EAS) puts a tag or strip on the goods and an antenna at the exit; if someone walks through with the tag still active, an alarm sounds. There are several systems (acousto-magnetic, electromagnetic, radio-frequency), all with a tag attached to the item, not the shelf.

An ESL sits on the shelf, not on the item, and sets off no alarm. Wikipedia notes that modern label systems sometimes integrate surveillance, digital signage and people counters, but that describes some manufacturers’ catalogues, not the price ESL as such.

It is not a tablet or digital signage

An electronic shelf label has a low-power display with a slow refresh, designed to show text and numbers for weeks without power. It does not play video or respond to touch. Digital signage (large LCD screens) is a different product, with a different purpose and power draw; it is covered separately in the glossary.

Differences at a glance

	Electronic shelf label (ESL)	RFID	Anti-theft (EAS)
Function	Show price and data	Identify and count objects	Detect leaving without paying
Where it goes	On the shelf	On the item or pallet	On the item
Has a display	Yes	No	No
Who starts the communication	The system sends data to the label	A reader interrogates the tag	An antenna detects the tag
What the store needs	Gateways and software	Readers and software	Antennas at the exit

Why the displays are e-paper

Most current ESLs use e-paper, a display that only needs power when the image changes. Because a product’s price changes only a few times a day, average consumption is tiny. That is why the battery can last years, and also why the display is readable in daylight or store lighting with no backlight. LCD models exist and make sense in specific cases, such as cold rooms or low-light environments; the details are in the article already cited.

A short history

Electronic shelf labels are not new. Their history, in three stretches:

• The 1990s: first systems. According to Pricer, in the early 1990s the Swede Erik Danielsson set out to digitise retail from his office in Uppsala, with labels based on wireless optical communication. SES, the French company now called VusionGroup, was set up in 1992. Wikipedia describes seven-segment LCD tags, like a calculator display, that received data by infrared, and a 1997 NCR system that used radio backscatter to confirm price changes without an active transmitter in the tag. That is what pushed battery life past five years.
• From infrared to radio and e-paper. By around 2016, according to Wikipedia, ESLs already combined e-paper and radio, and were being integrated with article surveillance, digital signage and people counters.
• Bluetooth 5.4: a standard profile. Bluetooth Core 5.4 adds Periodic Advertising with Responses, and the Bluetooth SIG builds a dedicated shelf-label profile on top of it. Any manufacturer can implement it, although manufacturers with their own radio remain on the market. A standard existing does not mean all equipment is interchangeable; vendor lock-in is a separate topic.

Who uses them

They are used in every kind of store and anywhere a displayed price changes with some frequency: supermarkets, hardware stores, electronics shops, wine merchants, bookshops, petrol stations. The reasons vary by sector. In grocery, what matters is how often prices change and unit-price control; in electronics or DIY, the number of SKUs; in fashion, the turnover of collections. There is no single calculation valid for all of them.

Which chains have rolled out ESLs in Spain is information that changes over time, so it is kept separately in the tracker of who uses electronic shelf labels in Spain. Pharmacies have a page of their own because of their management software and regulation: electronic shelf labels in pharmacies.

What to be clear on before going further

1. An ESL does not correct data. If the source price is wrong, the label will repeat it. Checking the data is work that comes before the project.
2. The system is the sum of four pieces, and each can come from a different vendor or the same one. That decision affects maintenance and how easy it is to switch supplier.
3. The radio and the battery define daily life: gateway density, listening interval and battery life are linked to each other.
4. The cost is not in the label, or not only. There are gateways, software, integration, installation and linking. The breakdown, with ranges and sources, is in the price guide.
5. Comparing with paper means measuring. The saving depends on the number of price changes and the time each one costs today; to compare with your own data, see the article on electronic shelf labels versus paper.