Open Source POS Software
A point-of-sale terminal has one requirement most checkout systems quietly fail: it has to keep ringing up sales when the network drops at the busiest hour of the day. A register that freezes because a cloud server is unreachable is a line of walkouts, not just a software glitch. Open source POS software lets you run the register on hardware you own, often against a local database that keeps selling through an outage and syncs when the connection returns. Just as important, the sales, inventory, and tax records stay in a database you control, so refunds, end-of-day reconciliation, and the accountant's export are yours to query rather than trapped behind a per-register subscription.
Open Source Point of Sale
Web-based point of sale system for inventory, sales, invoicing, and reporting
NexoPOS
Web-based point of sale system with a responsive dashboard for stores on phone, tablet, or desktop
Kriolos POS
Open source Java desktop point of sale, a fork of uniCenta oPOS for retail checkout
Our picks
Two are mature and released; the third is an early build for anyone tracking the uniCenta lineage.
Broad web register for shops and cafes: Open Source Point of Sale Open Source Point of Sale is a browser-based register covering stock for items and kits, a sale register with transaction logging, quotations, invoicing, receipts, and cash up, plus barcode generation. It handles multi-tier VAT and GST, customer and supplier databases, gift cards, rewards, and even restaurant tables, with multiuser permission control. Run it on your own server or via the documented Docker setup.
Responsive dashboard POS: NexoPOS NexoPOS is a web POS built on Laravel, TailwindCSS, and Vue, with a responsive dashboard that works on phone, tablet, or desktop. Cashiers process orders at checkout, every sale lands in an orders list for receipts, refunds, and payments, and a REST API and module system extend it. Self-host it by running the install wizard, or run it on the official NexoPOS Cloud.
Desktop POS in the uniCenta lineage (early): Kriolos POS Kriolos POS is a Java desktop register that continues the uniCenta oPOS and OpenbravoPOS lineage, running offline-first against a MySQL or MariaDB database. It is honest about its stage: still in development, published only as pre-release alpha builds, so running it today means compiling from source. Worth watching if you want a desktop POS in that family rather than a web app.
Fitting a register to how your store actually sells
The register itself is where a POS earns or loses its keep, so weigh the checkout path before the admin screens. Cashiers need barcode scanning, fast product lookup, discounts, split tenders, returns, and receipt reprints, and the peripherals behind them, meaning receipt printers, cash drawers, scanners, scales, and card terminals, are usually the real limiting factor. A local desktop app such as Kriolos POS can behave better with peripherals and during outages, while a browser-based register like Open Source Point of Sale or NexoPOS is quicker to deploy and reach across the network. Verify your exact hardware works before you commit, because generic USB support is not a guarantee.
The data model behind products, inventory, and tax is the next filter, and where migrations most often derail. Retail needs variants, SKUs, barcodes, purchase orders, and stock counts; Open Source Point of Sale covers items and kits, multi-tier VAT and GST, and even restaurant tables, a broad starting point. Restaurants care more about menus, modifiers, and kitchen routing. Tax handling, meaning mixed rates, tax-exempt customers, inclusive pricing, and refund rules, is painful to retrofit once sales history exists, so confirm it matches your books early.
Then decide where the system runs and what happens when connectivity fails. A hosted option like NexoPOS Cloud is simple to access anywhere, but a store-local install keeps registers selling during an outage only if it is built for it. Payment processing deserves separate review, since card-present sales and PCI scope depend on the terminal integration, not the POS itself. This is a small category with one honest caveat: Open Source Point of Sale and NexoPOS are mature and released, while Kriolos POS is still an early, build-from-source alpha, so treat it as one to watch, not to open a store on today.
Related categories
Frequently asked questions
Will checkout keep working during an internet outage?+
Only if the software is built for offline or store-local operation. A desktop app like Kriolos POS runs against a local database and is offline-first by design, while browser-based systems such as Open Source Point of Sale or NexoPOS keep selling during an internet outage only when the server itself is on the store network. Test offline behavior with discounts, taxes, receipts, and returns, and remember card terminals may still need connectivity even when cash sales do not.
Which hardware should I verify before choosing?+
Test the exact devices you will use: receipt printers, cash drawers, barcode scanners, label printers, scales, customer displays, and card terminals. Generic USB support is not a guarantee, because printer command sets, drawer kick cables, scanner prefixes, and scale protocols differ. A desktop app such as Kriolos POS often talks to peripherals more directly than a browser tab. Run one full register lane as a pilot; it reveals far more than a feature checklist.
How do payment terminals work with open source POS software?+
Most of these do not touch card data themselves. They integrate with a processor, terminal, or gateway that handles authorization and tokenization, which keeps card numbers out of the POS and limits your PCI scope. Confirm the integration supports card-present sales, refunds, tips, and settlement reports for your processor. NexoPOS records payments and refunds against each order, but the actual card handling still depends on the terminal integration you connect, so validate it early.
Can these run more than one store?+
Some can, but check the depth before assuming it. True multi-store support means location-specific stock, registers, users, taxes, price lists, transfers, and reporting, not one shared inventory pool that gets messy to reconcile. NexoPOS leans on a web dashboard and REST API that suit central management, while a single-register desktop tool is rarely a clean base for many locations. Test how stock and sales sync between stores and headquarters before you roll out.
What should restaurants look for that retailers may not need?+
Table management, tabs, coursing, modifiers, combos, tips, void reasons, and kitchen tickets. A retail-style register can ring food sales but may not handle kitchen routing or server accountability cleanly. Open Source Point of Sale does include restaurant tables alongside its retail features, which helps a cafe or small eatery. Whatever you choose, test split checks, tax on prepared food, service charges, and printing to kitchen stations before a real service.
How are permissions and cash accountability handled?+
Use roles that mirror the floor: cashier, shift lead, manager, and administrator, so a cashier cannot change tax rules, delete sales, or edit a closed shift. Open Source Point of Sale provides multiuser access with permission control, and any POS you pick should log refunds, voids, discounts, and drawer opens. End-of-day reports should tie sales, tenders, and expected drawer amounts to a specific register and user, which is what makes a shortage traceable.
Which of these is ready to run a store today?+
Open Source Point of Sale and NexoPOS are mature, released projects you can install and operate now, one a broad PHP web register and the other a responsive Laravel dashboard with a hosted cloud option. Kriolos POS is different: it is an early, pre-release alpha that you build from source against your own database, continuing the uniCenta and Openbravo lineage. Treat it as one to watch or contribute to rather than to open a store on.