Does a web based POS work without internet?

This is the first question every shop owner asks about a browser-based till, and it is the right question. It is also the one where vendor answers are least trustworthy, because “works offline” is a phrase that covers four completely different things and every vendor picks the most generous one that is technically true of their product.

So here is the useful version: there are four levels of offline, they cost very different amounts to build, and almost every claim you will read is level one or two being described in language that implies level four.

The four levels

Level 1: the page stays up. The connection drops, the till does not go blank or bounce you to a login screen. You can see the basket you were building. You cannot do much with it. This is table stakes and every serious system does it.

Level 2: you can still look things up. The product list is cached on the device, so you can search, check a price, and add items to the basket while the connection is away. You still cannot complete the sale. This is genuinely useful, because most connection wobbles last seconds and this level means you barely notice them.

Level 3: the sale survives a wobble. You press complete during a blip, and instead of failing, the system waits, retries, and lands it when the connection returns. The customer sees a spinner for a few seconds. Crucially, a correct implementation of this cannot double-charge on the retry, which is a harder engineering problem than it sounds.

Level 4: you can sell through a real outage. The connection has been gone for forty minutes and you are still ringing up sales, which queue on the device and sync when the internet comes back. This is what most people mean when they say “works offline”, and it is much rarer than the marketing suggests.

Level 4 is expensive to build and genuinely difficult to build correctly, which is why so few systems have it. The hard part is not storing the sales. It is what happens when they come back.

Why level 4 is hard, and why that matters to you

Imagine two tills in your shop, both offline, both selling. There are three of an item left. Till A sells two. Till B sells two. Both sync. You have now sold four of three, and one of your customers is getting a phone call.

That is the whole problem in one paragraph. A queued sale is a promise made about stock the system could not check. Multiply it by two tills, or by a discount rule, or by a loyalty balance, or by a customer’s store credit, and every one of those becomes a small argument the system has to settle when it reconnects, usually with no good answer.

Systems that do level 4 properly have made deliberate choices about all of those arguments, and they will tell you what they are. Systems that claim level 4 casually have usually not thought about it, which is worse than not having the feature: you get the sales back, and you get a stock figure you can no longer trust.

This is why it is worth knowing which level you are buying. Level 3 with an honest warning is a better product than a shaky level 4, and for most small shops it is also sufficient.

Which level do you actually need?

Be honest about your own connection rather than about connections in general.

Measure it before you decide. For two weeks, whenever the internet goes, write down the time and roughly how long it was out. Two lines on a pad by the till. At the end of the fortnight you will know something you currently only have a feeling about, and the feeling is usually worse than the reality because you only remember the bad ones.

Then:

• Outages of a few seconds, a few times a week. Level 2 or 3 covers you completely. You will not notice them.
• Outages of a minute or two, occasionally. Level 3 covers a sale in flight. For the rest, you take the card payment on the terminal and ring it up when the connection returns. Slightly annoying, not a crisis.
• Outages of half an hour or more, regularly. You need level 4, or you need a locally installed system. Do not let anyone talk you out of this. It is your building and your experience of it.
• No connection at all at the point of sale. A market stall with no signal, a van, a festival pitch. This is level 4 or nothing, and you should be shopping specifically for it.

And check your fallback, because it changes the answer. If your phone gets a good signal in the shop, then tethering the till to it is a five-second recovery from a router problem, and a router problem is the most common kind of outage there is. A shop with reliable mobile signal needs much less offline capability than its broadband reliability alone would suggest.

How to test a vendor’s claim in ten minutes

Do not ask. Test. Every one of these takes a minute and you can do all of them during a free trial.

1. Open the till, then turn off the wi-fi. Does the page stay up? Can you still search products and add them to a basket? That is levels 1 and 2, answered.
2. Build a basket, turn the wi-fi off, press complete, count to ten, turn it back on. Did the sale land? Did it land once? Check the sales list. One sale is level 3 working properly. Two sales is a bug you have just found for free, and it is a serious one. An error message is level 2, which is honest.
3. Turn the wi-fi off and try to complete a sale from scratch. If it succeeds and appears in the sales list only after you reconnect, that is level 4. If it refuses, that is the answer, and now you know.
4. Ask the follow-up question in writing. “If I queue sales offline on two tills and both sell the last item, what happens?” A vendor with a real answer will give you one. A vague answer means the feature exists but the thinking behind it does not.
5. Check what happens to the receipt. If you cannot print during an outage, can the customer be emailed one later, or do you write it by hand?

That fifth one catches people out. Printing usually depends on the local machine rather than the internet, so it often keeps working, but confirm rather than assume.

What to do during an outage, whatever your system

Have this written down and stuck somewhere near the till before you need it, because the moment you need it is the moment nobody can think.

1. Take the payment. Your card terminal is on a different network from your POS, usually mobile or a phone line, so it very often still works when your broadband does not. Cash obviously still works.
2. Write it down. Items, quantities, total, payment method. A pad by the till. This is the whole contingency plan and it costs nothing.
3. Tell the customer honestly. “Our system is down, I will write your receipt by hand.” Nobody minds. People mind being told to wait indefinitely with no explanation.
4. Ring them up when it comes back. Then check the stock figures for what you sold, because an accurate stock number is the thing an outage quietly damages.

A shop that has done this once treats a dropped connection as a nuisance. A shop that has not treats it as an emergency.

Where StoreWave sits

StoreWave is level 3, deliberately and explicitly, and it is worth saying that plainly rather than using the word offline and hoping.

The product catalogue is cached on the device, so a connection blip leaves the till usable rather than blank and the cashier keeps seeing and searching products. A sale in flight retries automatically with backoff, and a banner tells you it is reconnecting rather than leaving you guessing. Each order carries a client-generated key, so a retry that lands twice is recorded once: the double-charge in test two above cannot happen. The app itself is cached too, so it opens on a device with no connection instead of showing a browser error.

What it does not do is queue sales through a long outage. That is level 4, it is a separate piece of work, and it is not built. If your fortnight of notes says you lose the connection for half an hour at a time, StoreWave is the wrong choice for you today and a locally installed system is the right one. We would rather tell you that here than have you find out on a Saturday afternoon.

If your outages are seconds and your phone gets a signal in the shop, none of this will ever come up. That is most shops, but it should be a fact you have checked rather than one you have been told.