NFC tags

A tag works straight out of the packet — blank, read-only, or already written for something else. The trigger matches on the tag’s factory-burned hardware id, so there is nothing to write and nothing to configure on the tag itself.

Two platform limits

Both belong on this page rather than buried anywhere, because both look like bugs:

• There is no background tag scanning at all. A tag is dispatched to an Activity or to nobody, so a tap cannot reach a phone whose screen is off or locked.
• An app cannot switch the NFC radio on. NfcAdapter.enable() is system-only, which is why there is no Toggle NFC action.

Peer-to-peer (Android Beam) was removed in Android 14, so there is no phone-to-phone half to build either.

The trigger

NFC Tag with no tag chosen matches any tag. That is a deliberate answer, not a job half-done, and the field says “Any tag” rather than “None selected”.

Choose a tag and it matches that one.

The library

Setup → NFC tags maps a hardware id to a name. It is cosmetic: the uid is the key, so re-scanning a sticker updates its row rather than adding a second, and deleting a row costs a node its tag name and nothing else — the tap still matches.

That is why there is no Problems entry for a tag that has been deleted, unlike a deleted variable or macro. A rename reaches an already-armed macro without a re-arm.

The tag chooser produces its options rather than listing them: a tag you have never scanned is in no list, so opening it starts a capture — hold a tag to the phone and it appears, with your saved tags above.

Writing tags

The Tags screen can write a tag, which exists to make it useful to other apps and to give the trigger’s text output something to carry. It is deliberately not on a node and not inside the capture chooser — two reader-mode registrations would fight.

The value node

NFC enabled answers whether the radio is on. It declares no permission, on purpose: a node whose whole job is to answer “is the radio on?” must never be badged in the Problems panel for the radio being off. That is the node working.

The prerequisite belongs on the trigger, which genuinely cannot fire without it.

There is no “when NFC is switched on” trigger, because the platform publishes no broadcast worth arming a macro on.