The tag reads but opens the wrong thing
Usually an old record still present, or several records where the phone acts only on the first. Writing new content does not necessarily remove what was there, and a tag holding two addresses will pick one without asking you which.
The phone acts on the first record
A tag can hold several records, and the operating system acts on the first one it finds that it knows how to handle.
So a tag with two web addresses opens one of them, consistently, and the choice is made by position rather than by intent.
This is normal behaviour rather than a fault, and it defeats the common idea that stacking records gives the user a menu. It does not.
If you need a choice, put one address on the tag and let the page it opens offer the options.
Old content that was never removed
Writing a shorter message over a longer one does not always leave the tag holding only the new message, depending on the tool and what it does with the remaining space.
More often the problem is simpler: a second record was added rather than replacing the first, and the tag now holds both.
Read the tag and count the records. Two records where you expected one explains the symptom completely.
The same applies to a tag reused from a previous project. What it held before is still there unless something removed it.
When another app claims it
If the content is a web address that an installed application registers for, the phone may open that application instead of a browser.
That is the operating system working as designed, and it is why a tag tested on a clean phone can behave differently on a phone with more apps installed.
Test on a device that resembles your audience rather than on your own, which is likely to have unusual software on it.
Getting back to a known state
Erase the tag, then write the single record you want, then read it back and confirm exactly one record is present.
Reading back is the step that matters. It is the only way to know what the tag holds rather than what you intended to put on it.
If the tag is locked, none of this is possible and the content is final. Check that before spending time on it.
And when preparing a batch, verify a sample against the expected record count as well as the expected content. A batch where every tag carries an extra record is a batch written with the wrong option selected.
Frequently asked questions
Can I choose which record runs?
Only by ordering them, since the phone acts on the first it can handle. There is no way to present a choice from the tag itself.
Does writing erase the old content?
It replaces the message, and adding a record rather than replacing one is a common mistake. Read the tag back and count the records.
Why does it open an app instead of my page?
Because an installed application registered for that address. This is normal, and it makes testing on a typical device more useful than testing on yours.
How do I remove everything from a tag?
Erase it with a tool that clears the content, then read it back to confirm it is empty before writing again.