How do you link a tag to a smart home system?
Through one of two routes. Either the phone recognises the tag and runs an automation it holds, or the tag opens a web address your system answers. The first is easier to set up and the second survives a change of phone, platform or person.
Two routes
In the first, the phone is configured to recognise a particular tag and to run something when it sees it. The tag is an identifier and the logic lives on the phone.
In the second, the tag holds a web address, and asking for that address is what triggers the action. The logic lives on a server or on your home system.
Both end with the same lamp turning on. What differs is where the intelligence sits, and therefore what breaks it.
The phone side route
Set up entirely within an application on the phone: recognise this tag, perform these steps.
Quick to build, needs no address and no server, and it can use anything the phone can do rather than only what your home system exposes.
It is also personal. The automation exists on that phone and nowhere else, so a second person tapping the same tag gets nothing.
And it does not survive a new phone unless you rebuild it, which people discover at the worst moment.
The address route
The tag holds a short address. Opening it reaches something that instructs your home system.
It works for anyone who taps, including guests and family, because nothing has to be configured on their phone.
It survives a change of phone entirely, and a change of platform if the address is yours and only the destination changes.
The cost is setup: you need a home system that can be instructed this way, and an address that is not guessable by anyone who wanders past.
Choosing between them
Personal, on your own phone, changing often: the phone side route, and accept rebuilding it occasionally.
Shared, in a household, meant to last: the address route, and put the address on a domain you own.
Anything a guest should be able to use: the address route, since it is the only one that works for somebody who installed nothing.
And for anything security relevant, neither without thought, because a tag on a wall is readable by anyone who reaches it.
Frequently asked questions
Which route is easier?
The phone side route, set up entirely in an application. It is also personal to that phone and does not survive replacing it.
Can a guest use my home tag?
Only with the address route, since it needs nothing configured on their phone. A phone side automation exists on your phone alone.
What happens when I change phone?
A phone side automation has to be rebuilt. An address based one carries on working, because nothing about it lived on the phone.
Is a guessable address a risk?
Yes, if it performs an action. Anyone who reads the tag has the address, so treat it as public and design accordingly.