NFC · NDEF · Type 4 tag
Your phone as an NFC tag – read-only or writable
An NFC memory card turns your phone into a standard NFC tag. A read-only card holds what your organisation put on it – a link, a text or an ID – and any NFC reader or phone can read it. A writable card lets a reader write to it, for example a check-in desk or a smart-home reader. Only the card you choose answers, and only for five minutes. Details: read-only NFC tag · writable NFC tag.
- Standard NFC tag
- Read-only or writable
- Works with Home Assistant
What you need
An Android phone with NFC, CodeB Wallet and an NFC memory card your organisation issues through phone.codeb.io – read-only or writable.
How to use it
- Collect the NFC memory card from your organisation. It appears in your wallet.
- Open the card and tap Use at reader – or tap Hold to reader when the card is in front on the home screen.
- Hold your phone to the reader or the other phone and keep it unlocked.
- Tap Stop when you are done – leaving the screen ends it as well.
What can read it
Anything that reads standard NFC tags (NFC Forum Type 4 tag with NDEF content), for example: another Android phone or an iPhone, NFC apps such as NFC Tools, the Home Assistant app, check-in and visitor terminals, and USB or industrial NFC readers that support Type 4 tags.
Home Assistant: put a Home Assistant tag link (https://www.home-assistant.io/tag/…) on the card – or, with a writable card, let the Home Assistant app write it. An Android phone or wall tablet with the Home Assistant app reads the tag, and an automation can switch lights, start a scene, unlock a smart lock or switch a Shelly relay that opens an electric door strike, a gate or a garage door.
Not every reader reads phones: ESPHome readers (PN532, PN7150) and many simple card readers read only plastic tags such as NTAG213, NTAG215, NTAG216 or MIFARE – they do not read the tag on a phone. For Home Assistant use the Home Assistant app on an Android tablet at the door.
Smart locks
Smart locks do not read NFC tags from a phone directly. We checked the manufacturers’ documentation: Nuki opens with its app and Bluetooth (Nuki Keypad 2 NFC uses the Aliro standard), Yale and August with their app, Bluetooth, a PIN or their own key tags, igloohome with PIN codes, Bluetooth and its own RFID tags, TTLock locks with the app, a PIN or IC cards, Aqara and SwitchBot with their own NFC cards or MIFARE Classic cards, and dormakaba Oracode with time-limited PIN codes. Their card readers recognise a plastic card’s chip and fixed serial number, which a phone cannot imitate.
With Home Assistant it works: connect the lock to Home Assistant – for example Nuki, Yale, August or SwitchBot, or any Matter, Zigbee or Z-Wave lock – put an Android tablet with the Home Assistant app at the door, and let an automation unlock the door when your phone’s tag is read. Doors with an electric strike, gates and turnstiles open the same way through a Shelly relay.
Keep in mind: whoever reads a tag can copy its content. For doors that need real security use the CodeB Access card – it answers with a fresh signature from a key in the phone’s secure hardware and works with PKOC door readers.
Writable cards
With a writable card a reader – or another phone with an NFC app – writes its content to your phone. CodeB Wallet stores it encrypted on your phone, lists every write and lets you restore the original content.
Only when you choose
Only the card you chose answers, for five minutes, and only while your phone is unlocked. While the card is ready your phone acts only as this tag: it does not offer your ID and does not read other phones. It never interferes with payment apps or your other cards.
Questions about the phone as an NFC tag
Can my phone act as an NFC tag?
Yes. With an NFC memory card in CodeB Wallet your Android phone answers as a standard NFC tag (NFC Forum Type 4, NDEF) – a link, a text or an ID.
What is the difference between read-only and writable?
A read-only card always shows what your organisation put on it. A writable card lets a reader write new content, which CodeB Wallet keeps encrypted on your phone; you can see every write and restore the original.
Can it open my Nuki, Yale, igloohome or TTLock lock?
Not directly – these locks do not read NFC tags from phones. With Home Assistant it works: an Android tablet with the Home Assistant app at the door reads the tag and an automation unlocks the lock. For secure door access use the CodeB Access card.
Does it work with Home Assistant?
Yes. Put a Home Assistant tag link on the card or let the Home Assistant app write it to a writable card; the Home Assistant app on an Android phone or tablet then reports the tag to your automations. ESPHome readers (PN532) read only plastic tags, not phones.
Does it work with a Shelly relay?
Yes, through Home Assistant: when the Home Assistant app reads the tag, an automation switches the Shelly relay that opens an electric door strike, a gate or a garage door.
Can someone copy it?
Whoever reads the tag can copy its content, as with any NFC tag. Use it for convenience; for security-relevant doors use the CodeB Access card.
Install the test version (Google Play) Closed beta: works only for invited testers who are signed in to Google Play with the e-mail address we have on our tester list.