What kind of NFC-Tag is only readable in Shortcuts App?

Question

I just got my iPhone 11 pro max and wanted to see, if it can read the nfc enabled wrist band of my local gym. There are several nfc-apps[1] on the app store and additionally the shortcuts app is capable of reading nfc-tags.

When scanning the wrist band with the shortcuts app, it is recognized. But every other app does not recognize it.

Are there different flavors of nfc? Is this just a iOS quirk? Is there a reason why only the shortcuts app can see this tag?

Background:

The local gym has some kind of nfc-based member-card. In fact its not a card, but a wrist-band with a tiny nfc-chip in it as it seems. The wrist band reader on the door is made by a company named "Gantner".

In the long run I want to get rid of this silly red wrist band and just use my apple watch. But I think this is not (yet) possible. Nevertheless I am curious to understand what is stored in this band and how nfc works in this case.

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Update: Added Apps

[1] NFC for iPhone, NFC-Tools, NFC21 Reader, Simply NFC, NFC TagInfo and a few others.

Answer 1

NFC is a standardized set of protocols - so in that sense "NFC is NFC". However the standard allows for multiple types of tags (i.e. your wrist band has an NFC tag embedded in it).

Currently the standard allows for 5 different types of tags, which vary in speed, capacity, mode settings, etc. For example you can set tags to be read-only or rewritable, and some types allows you to change from read-only to rewritable and vice versa, and others do not.

On top of that, NFC tags are produced by many different companies, allowing you to pick from a huge variety of form factors (dimensions, weights, etc) in various materials.

However the reason your tag is not readable by other apps is not because of these differences, nor that iOS has quirks.

It is simply so that apps tend to limit the tags that they scan to the ones associated with that app. I.e. no need to scan any random tags, if you're only interested in very specific ones. The phone actually scans every tag, but the app filters those out it is not interested in.

The Shortcuts app allows you to use more or less any tag - so it will do just that.

Update: You have updated your question indicating the specific apps you have used. You have tried to use generic apps that should read "any" tags - and thus app specific filtering is not your problem.

However your problem is instead that on iOS 12 and prior, the system allowed apps to read only tags encoded in the NFC Data Exchange Format (NDEF). Your tag must likely is not encoded in NDEF, and thus cannot be read by those apps.

On iOS 13 that limitation has been lifted. However, app developer must change their apps to expand the types of data encodings they can read. Those app you have tried aren't updated to read the specific type of tag you have.

Answer 2

NFC tags come in different Tag Types, which have a Signalling Type and support a Protocol, like so:

Tag Type	Type 1	Type 2	Type 3	Type 4
Signalling Type	NFC A	NFC A	NFC F	NFC A or NFC B
Protocol	Topaz	MiFARE Ultralight	FeliCa	ISO-DEP

In my recent experience with an iPhone 13 running iOS 16.6.1, NFC21 Tools and NFC Tools are able to detect an Opal public transport card (Type 4A). They are not able to detect two different door bracelet tags (Type 2) like the ones you describe.

The Shortcuts app is able to detect all three.

I note that Shortcuts seems only concerned with the ID of the tag, so perhaps does not attempt protocol communication and is satisfied with just getting the ID during the anti-collision process (which is common across NFC A).

Therefore I posit (thus only an answer proposal) that the Shortcuts app can detect any tag which passes anti-collision and reveals its ID. The other apps attempt to read data from the tag, and perhaps fail unless they talk ISO-DEP.