In order to access the cards, you must following two steps: 'Connect' to a Mifare Ultralight card and retrieve the 7 byte UID of the card. Memory can be read and written directly once a .NFC Tools Online. NFC Tools Online. NDEF NFC Tag Reader Write Text to NFC Tag Write URL to NFC Tag Write WiFi to NFC Tag Write Android App Text to NFC Tag. Online tools to read and write the data on your NFC tags.