The sticker on my card is an NFC chip. Tiny antenna, microchip, ~500 bytes of memory. Your phone got close, powered the chip, and it sent you here. No battery. No pairing. Just proximity.
That sticker? It's yours now. You can't steal what's a gift. Peel it off, stick it wherever you want, and reprogram it to do literally anything. Keep reading to find out how.
"A sticker that runs code when you touch it."
-- The NFC Desk, being dramaticNFC stickers, cards, keychains. NTAG215 is the sweet spot. Amazon, Flipkart, AliExpress. Dirt cheap.
You need an app to write records to the chip. Use one that works:
Open app, pick record type, fill details, hold chip to back of phone, wait for the vibration. Done.
Most apps let you lock the chip so nobody overwrites it. Good for public chips. Skip for ones you want to reprogram.
Pick a category to see the NFC record structure, or type your own idea.