[walterbell]

The cheapest RFID/NFC "card" tag is an expired tap-to-use transit ticket. It has a unique ID that can be used to trigger an iOS Shortcut to take any action, e.g. speak an audio description, open URL, open app, etc.

For purchase, there are many form factors: https://store.gototags.com/nfc-tags

On Amazon, search NTAG215.

[immibis]

If your city doesn't use NFC transit, you can also buy a box of blank cards. They have unique IDs like transit tickets, even without being programmed.

[stavros]

NTAG215 isn't "magic", right? I have a bunch of NTAG215 stickers and I'm not entirely sure what their difference is with magic cards.

[ewpratten]

Think of it like a subset of MIFARE.

In a simple sense, NTAG cards can do NFC things, but MIFARE can do lots more (access control for example)..and also NFC things..somewhat.

Magic mifare refers to special cards that let you bypass the write-lock of genuine mifare cards. These are mostly used for cloning keys (either for red-team pentesting or for people who want a copy of an office key for whatever reason)

[lxgr]

It's not really a subset:

MIFARE Classic uses a proprietary and mandatory encryption/authentication algorithm and is therefore not ISO 14443-4 compliant. As a result, NFC-compliant readers don't need to support it, and in fact non-NXP ones (including many popular Android phones) usually don't.

On the other hand, as you say, MIFARE Classic supports capabilities beyond NFC/NDEF, but there are fully NFC-compliant tags that do so as well (e.g. MIFARE DESfire, which properly stacks encryption in an ISO 14443-4 compliant way).

[stavros]

Ah, thanks, so I guess to write tags like URLs and things I don't really need Mifare cards, the NTAG cards are fine. Thanks for the info!