James Whitfield
I was in Warsaw last spring visiting a client, and I noticed something that completely changed how I think about last-mile delivery. Every few blocks, there was a bright yellow InPost locker. Outside grocery stores. Next to tram stops. Tucked into apartment building courtyards. They were everywhere.
My client told me something that floored me. Roughly seventy-two percent of Polish online shoppers have used InPost lockers. And a significant chunk of them will straight up abandon their cart if locker delivery is not available at checkout. Not "prefer" lockers. Will leave without buying.
That is not a nice-to-have feature. That is table stakes.
Why lockers are winning
The economics work for everyone. For customers, lockers mean no waiting around for a courier, no missed delivery attempts, and twenty-four-seven pickup availability. Grab it on your evening walk. Pick it up at two in the morning if you want. Nobody cares.
For merchants, the savings are real. Locker delivery in Poland typically costs thirty to forty percent less per parcel than traditional door-to-door courier service. When you are shipping thousands of parcels a month, that difference adds up to serious money.
But there is a behavioral shift happening too that goes beyond cost. People in dense European cities genuinely do not want to be stuck at home between ten and six waiting for a package. They want flexibility. InPost understood this early, and their network density in Poland - over twenty thousand machines - means there is almost always a locker within a five-minute walk.
This pattern is spreading fast. InPost now has thousands of lockers in the UK and is growing aggressively in France and Italy. If you are building cross-border e-commerce infrastructure, locker delivery is becoming a requirement, not an option.
What makes locker integration different
Here is where things get interesting from a technical perspective. I have integrated plenty of standard courier services, but locker delivery introduces concepts that door-to-door shipping simply does not have.
First, locker selection. The customer needs to pick a specific locker during checkout. This means you need some kind of locker finder - either a map widget or at minimum a search by postcode. InPost provides their own widget, but embedding it properly into your checkout flow takes real work.
Second, size constraints. Lockers have physical compartments in three sizes. The smallest is roughly 8 by 38 by 64 centimeters. The medium is about 19 by 38 by 64. The largest is around 41 by 38 by 64. Your shipment absolutely must fit. There is no "we will figure it out" option. If the parcel does not fit the compartment, it gets rerouted and the customer experience suffers badly.
Third, pickup deadlines. Customers get forty-eight hours to collect their parcel. After that, it goes back. Your system needs to handle the notification flow and potential returns gracefully, or your support team will be drowning in tickets.
Using UniShip for InPost integration
You can integrate InPost directly through their own API. For some teams that makes sense. But if you are already shipping with other carriers - or plan to - integrating InPost through UniShip means you get one API for everything.
The way it works is straightforward. You send a shipment creation request to our Shipment API specifying InPost as the carrier, include the recipient's chosen locker ID and parcel size, and the response comes back in our standard format. Same structure as a DHL or DPD shipment. Same fields, same tracking format, same label download process.
That consistency is the whole point. Your code does not need to know whether it is talking to InPost, DHL, or any other carrier. UniShip handles the translation.
Finding lockers with the PUDO Map
For the checkout experience, customers need to find and select a locker. Our PUDO Map - that stands for Pick-Up Drop-Off - provides a unified interface for locker and point selection across carriers. Not just InPost, but also DHL ServicePoints, DPD Pickup locations, and others.
You give it a location - coordinates or a postcode - and a radius, and it returns nearby lockers with availability status, operating hours, and compartment size availability. Most InPost lockers run twenty-four-seven, but the API tells you for certain. You can embed this directly in your checkout or build your own interface on top of the data.
I have seen some really elegant checkout implementations where the customer types their postcode and immediately sees a map with available lockers, color-coded by how close they are. It takes maybe ten seconds for the customer to pick one. That kind of smooth experience drives conversion.
Hard-won lessons from production
After working with merchants who process tens of thousands of InPost shipments, I have collected a few lessons that you will not find in any official documentation.
Validate phone numbers aggressively. InPost sends SMS notifications to the recipient with the pickup code. A wrong phone number means the customer never gets their code, never picks up their parcel, and your support team gets an angry ticket forty-eight hours later. Make sure it is a real Polish mobile number. This single validation check prevents a surprising number of problems.
Handle the oversized case gracefully. If a customer orders something that does not fit in any locker compartment, do not just show an error. Offer a fallback - InPost courier delivery or another carrier entirely. Build this into your carrier selection logic from day one, not as an afterthought.
Monitor locker capacity during peak seasons. Popular lockers in city centers can fill up, especially around Black Friday and Christmas. If a specific locker is full, the parcel might get rerouted to a nearby one. Your tracking notifications need to account for this so the customer knows which locker to actually visit.
Set delivery expectations correctly around weekends. InPost lockers operate around the clock, which is one of their biggest advantages. But the logistics network behind them does not. Parcels created on Friday might not arrive at the locker until Monday. Communicate this clearly and you will avoid a flood of "where is my package" messages every Monday morning.
The business case in numbers
For anyone who needs to justify adding InPost locker delivery to their platform, here are the numbers that matter.
Average delivery cost runs twenty-five to forty percent less than door-to-door courier service in Poland. The first-attempt delivery rate is essentially ninety-nine percent - because it is a locker, there is no "not home" problem. Average pickup time from notification is about six hours. Customers are fast when they know exactly where to go.
Some merchants I work with have also reported two to three percent lower return rates with locker delivery. The theory is that the small friction of having to walk to a locker to return something makes impulse returns less likely. I am not entirely sure about the causation there, but the correlation is consistent across multiple clients.
If you serve the Polish market - or plan to expand into it - InPost integration is not optional anymore. It is expected. And with UniShip, you can add it alongside all your other carriers through a single integration. No separate API, no separate credentials, no separate label format to worry about.