The NDEFReader interface of the Web NFC API is used to read from and write data to compatible NFC devices, e.g. NFC tags supporting NDEF, when these devices are within the reader's magnetic induction field.

NDEFReader() Experimental

Returns a new NDEFReader object.

The NDEFReader interface inherits the methods of EventTarget, its parent interface.

NDEFReader.scan() Experimental

Activates a reading device and returns a Promise that either resolves when an NFC tag read operation is scheduled or rejects if a hardware or permission error is encountered. This method triggers a permission prompt if the "nfc" permission has not been previously granted.

NDEFReader.write() Experimental

Attempts to write an NDEF message to a tag and returns a Promise that either resolves when a message has been written to the tag or rejects if a hardware or permission error is encountered. This method triggers a permission prompt if the "nfc" permission has not been previously granted.

Inherits properties from its parent, EventTarget.

reading Experimental

Fires when a new reading is available from compatible NFC devices.

readingerror Experimental

Fires when a tag is in proximity of a reading device, but cannot be read.

The example below shows how to coordinate between a common reading handler and one used specifically for a single write. In order to write, a tag needs to be found and read. This gives you the ability to check whether it is actually a tag that you want to write to. That's why it's recommended that you call write() from a reading event.

const ndef = new NDEFReader();
let ignoreRead = false;

ndef.onreading = (event) => {
  if (ignoreRead) {
    return; // write pending, ignore read.
  }

  console.log("We read a tag, but not during pending write!");
};

function write(data) {
  ignoreRead = true;
  return new Promise((resolve, reject) => {
    ndef.addEventListener(
      "reading",
      (event) => {
        // Check if we want to write to this tag, or reject.
        ndef
          .write(data)
          .then(resolve, reject)
          .finally(() => (ignoreRead = false));
      },
      { once: true },
    );
  });
}

await ndef.scan();
try {
  await write("Hello World");
  console.log("We wrote to a tag!");
} catch (err) {
  console.error("Something went wrong", err);
}