Can you make your own QR code pet tag? What to know first

A static QR code holds the information itself, such as your phone number or a web address. It keeps working for ever, but it can't be changed: a new phone number means a new tag.

A dynamic QR code holds a short link to the QR website's own server, which sends the phone on to your page. You can change where it goes, but it only works for as long as that website keeps it switched on.

Many QR code websites offer dynamic codes on a free trial, and switch them off when the trial ends unless you pay. QR Code Generator's own help pages, for example, say that when its free trial expires, dynamic codes are deactivated and point to a service page instead, while static codes keep working.

On a pet tag, that's the worst way for a code to fail, because nobody finds out until a stranger scans it. If you make your own, choose a static code, or a service that says in writing that its free codes never expire.

• Put your phone number in as plain text, or link to a page that you control and will keep up to date.
• Make it as large as the tag allows, dark on a light background, with a clear margin all the way round.
• Test it with two or three different phones before you print it, and again once it's on the tag.
• Protect it. Paper and printed stickers fade, scratch and get wet on a collar, so check it every few weeks and replace it when it's worn.

• Keep your number private: anyone who scans a code with your number in it can see it.
• Tell you it's been scanned, or roughly where.
• Let a finder message you and share their location without you giving out your details.
• Change what it says without a new tag, unless it's a dynamic code, with the risk above.

In the UK, a dog in a public place must wear a collar with its owner's name and address on it, or on a tag attached to it. A QR code, homemade or bought, doesn't meet that on its own, so it goes alongside an engraved tag, not instead of one. Our guide to UK dog tag law has the details.

A PetTag is the ready-made version. The code is set into a tough 40 mm tag and opens your pet's page, which you can change any time. Finders can message you without seeing your number, and lost mode emails you when the tag is scanned. It's £10, paid once, with no subscription, so nothing switches off when a trial ends.

Any tag that links to a web page depends on that website staying up, ours included. That's one more reason to keep an engraved tag with your name and address on the collar too.