There's lots of info about the NDEF "packet" format online.

I used this page as reference when I was putting together the "magic bytes" in the final section of the blog post: https://www.oreilly.com/library/view/beginning-nfc/978144932...

This is fantastic, thanks!

Also, one thing that might be of interest: Even after a wipe and an ndefformat, my Android-written tag can be read by my iPhone 15.

NFC tools will only read it in compatibility mode, though.

Are you sure? The NFC app for iPhone can always read tags. Its specifically getting phones without the app to read them.

Try wiping, then writing a URL from Android.

Then just tap to the iPhone and see if Safari opens or not. It shouldn't

Yes:

https://imgz.org/i9ZqL6Ax.png

I don't know if it's Vivaldi doing that, but I can't imagine they would have added NFC tag reading capability to the browser specifically.

Feel free to email me if you want, btw, as this thread is getting a bit too deep.

If a URL is written using NFCTools on iPhone, iOS will open it in the default browser without using NFCTools, or in the related app (eg Instagram) if there is one.

I find this only to be true when used on the same iPhone where NFCTools was used.

If you try to have another iPhone detect the badge, it appears not to work - unless you use NFCTools on that iPhone, too. I don't have conclusive proof but that's what the evidence seems to indicate.

Are you seeing something different?