Partly. The code will scan anywhere, including in a field with no signal at all. The page it points to needs an internet connection to load.
That is the honest answer, and it matters, because a great many British cemeteries and country churchyards have poor mobile coverage. It is worth understanding properly before you choose where to put a plaque, and it changes what you should have engraved on it.
Why the two halves behave differently
Scanning and loading are separate events, and only one of them needs the internet.
Scanning is entirely local. The camera reads the pattern and decodes it into text on the phone itself. No connection is involved, no server is contacted, and nothing leaves the device. A QR code is a piece of writing, and reading writing does not require a network. This works in aeroplane mode, in a cellar, on a moor.
Opening the page needs data. The decoded text is a web address, and fetching a web page means reaching a server.
So with no signal, here is what actually happens: the phone scans the code, recognises it, and offers the link. The visitor taps it. The browser opens and fails to load, showing the usual no-connection message.
Which is a real disappointment at a graveside, and worth designing around.
The good part
The link does not vanish. It is now in that person's browser history and open in a tab.
In practice, most people drive out of the cemetery, regain signal a mile down the road, and the page loads then. Some notice it that evening. It is not the moment the family imagined, but the memorial is not lost, and this is genuinely how most no-signal scans end.
If the visitor has opened the page before, on that phone, some of it may load from the browser's cache even offline. Do not rely on it, but it is common enough to mention.
What to do about it
Four things, in order of how much they help.
1. Engrave the name and dates on the plaque.
The most important line in this article. A plaque carrying only a code is meaningless without signal, and meaningless to anyone who has no smartphone, which at a graveside is a substantial proportion of visitors.
A plaque carrying the name and the dates alongside the code always works. It works with no signal, no phone, no battery and no interest in technology. The code is then a bonus for those who can use it rather than the entire content of the memorial. This is the single strongest argument for adding engraving to your memorial plaque, and it is a resilience argument rather than an aesthetic one.
2. Check the signal before you commit.
Stand where the memorial will be and look at your phone. Better still, look at two phones on different networks, because coverage in rural areas varies enormously between operators, and it is entirely normal for one network to have four bars where another has none.
Ofcom publishes a mobile coverage checker for any UK postcode, which is worth ten seconds before you assume anything.
3. Prefer a short web address.
Short addresses help twice over. A shorter address means a sparser, more robust code, which scans more reliably through lichen, glare and dirt. And a short address can be typed in later by somebody who noted it down, whereas a long one cannot realistically be.
Where there is room, some families have the address engraved in small text beneath the code, so a visitor with no signal can photograph it and type it in at home. It also serves anybody whose phone will not scan for any other reason.
4. Think about where the memorial actually gets visited.
The remote hillside churchyard is beautiful and has no coverage. The bench in the town park has full signal, and gets sat on by two hundred people a week.
You do not have to choose. Plaques are inexpensive relative to everything else in this process, and several can point at the same page: one on the headstone, one on a bench, one on a frame at home. The rural one is the memorial. The others are where it actually gets read.
What about NFC?
Sometimes suggested as the fix. It is not.
NFC has exactly the same limitation, and for the same reason. The tag stores a web address and the phone still has to fetch the page. The tap works offline; the page does not load. There is no version of this technology that puts photographs inside a plaque.
NFC does have genuine advantages elsewhere, particularly its invisibility where a visible code would be refused. That comparison is in QR or NFC for a memorial.
Is it getting better?
Yes, slowly. UK rural coverage has improved steadily, and satellite-to-phone messaging has begun appearing on newer handsets, though it is aimed at text rather than browsing.
Over the life of a memorial, coverage is far more likely to improve than to worsen. A cemetery with poor signal today will probably have adequate signal within the lifetime of the plaque. It is a reason for patience rather than a reason to abandon the idea.
The short version
The code scans anywhere. The page needs data. Engrave the name and dates as well, so the plaque means something regardless, check the signal before you commit, and consider a second plaque somewhere people actually go.
A memorial that depends entirely on a phone working is a fragile memorial. One that carries a name, and offers more to anyone who can reach it, is not.