Square is the default answer for a shop that needs to take a card payment tomorrow. The reader arrives in a box, the app is free, and money lands in your bank the next business day. That is a genuinely good product, and if you have no website and no intention of building one, you should probably stop reading and buy it.
This comparison is for the other shop: the one already running WooCommerce, wondering whether to bolt Square onto it or put the register inside WordPress instead.
The difference that decides it
Square is a cloud platform that owns your payments. OpenPOS is a plugin that lives inside your WooCommerce database and owns nothing.
Everything else follows from that. With Square, your catalogue and sales history live in Square’s cloud, and the official WooCommerce Square plugin keeps the two systems talking through an API — you nominate one of them as the system of record and it pushes inventory to the other. That connector works, and Automattic maintains it, but it is a sync: there is a window between a shop sale and your website learning about it, and every product needs a matching SKU on both sides.
With OpenPOS the register writes a normal WooCommerce order directly. There is no interval, no SKU mapping, no second catalogue, because there is no second database.
Cost
| Square | OpenPOS | |
|---|---|---|
| Software | Free tier; Plus $49/mo per location; Premium $149/mo per location | One-time purchase, per site |
| Extra registers | Included in the per-location fee | Unlimited, no charge |
| Card processing | Square’s rails only — 2.5% + 15¢ (Plus), 2.4% + 15¢ (Premium) | Your own acquirer, at your own rate |
| Ongoing | Subscription, per location, forever | Hosting; optional support renewal |
Square’s free tier is real, and for a single till doing modest volume it is hard to argue with. The arithmetic changes with locations, because the fee is charged per location, and with card volume, because you cannot shop around for a better processing rate.
That last point is the one merchants underweight. On meaningful card turnover, a fraction of a percent in processing is a larger annual number than any POS licence. Square does not let you bring your own acquirer; its readers only speak to Square. OpenPOS takes no cut of anything and supports Stripe Terminal, Square Terminal, Authorize.net, BlockChyp, Clearent, Vipps and LayBuy, so you keep whatever rate you negotiated.
Where Square is genuinely better
Three things, stated plainly, because a comparison that finds no merit in the alternative is an advert.
- Offline card payments. Square’s offline mode stores card transactions on the device and settles them on reconnect, within a 72-hour window and a per-transaction cap you set. OpenPOS queues orders offline and syncs them, but a card payment still needs a processor that is reachable. If your line drops and you must take cards, Square does something OpenPOS cannot. You carry the decline risk either way.
- Nothing to run. No WordPress host, no updates, no backups, no PCI questionnaire beyond the simplest one. Square carries all of it.
- Payments that just work. Merchant account, gateway and hardware arrive as one decision instead of three.
Where OpenPOS is better
- One inventory. No connector, no sync interval, no SKU mapping. The oversell window that a sync creates does not exist.
- No per-location, per-register or per-transaction fee. A one-time purchase for the site. The fourth till costs a tablet.
- Your data. Orders and customers sit in your own MySQL database. You can query it, export it, or leave — there is nobody to ask.
- Restaurant mode included. Floor plans, table merge and transfer, kitchen display screens.
- Your processor. Keep your acquirer and your negotiated rate.
Which should you choose?
Choose Square if you do not have a WooCommerce store and do not want one; if offline card acceptance is non-negotiable; if you would rather pay a percentage than administer a server.
Choose OpenPOS if WooCommerce is already your shop; if you have — or expect — more than one till or one location; if your card volume makes processing rates matter; if you want the sales history in a database you control.
And note the option nobody mentions: run OpenPOS as the register and keep a Square Terminal beside it as an unintegrated card machine. You lose the automatic amount transfer, staff key the total in, and you keep both Square’s hardware and WooCommerce’s single inventory. Plenty of shops do exactly this.
Frequently asked questions
Can I use a Square reader with OpenPOS?
Square Terminal is a supported integration. A standalone Square reader can also sit beside the till as an external payment method.
Does OpenPOS charge per transaction?
No. You pay your payment processor and nothing else. There is no revenue share.
Is Square’s WooCommerce plugin any good?
It is first-party and actively maintained. The limitation is architectural, not a quality problem: two databases synced by an API will always have a window in which they disagree.
What happens if I stop paying for OpenPOS?
Nothing — the licence is one-time and includes updates. Only the support service, meaning a human answering your questions, runs for a period and can be renewed.
Square pricing above was read from Square’s own published pages in July 2026, US listings in USD. Prices, rates and offline limits vary by country and change over time — check squareup.com before deciding.
Ring up a sale on the live OpenPOS demo (admin / admin123), or read how one inventory removes the sync problem. OpenPOS is a one-time purchase with unlimited registers, or start with the free OpenPOS Lite on WordPress.org.