NFC tags can be read by RFID reader?

We just did some dirty experiment, and it seem it can be done.
We have been able to use a RFID reader to read an NFC tag.

Keep in mind that this is some 'dirty' experiment done 'as is' in a few minutes just to see if it's possible.

We used a RFID reader able to read the ISO 14443-A standard, the reader has been configured to read Mifare Ultralight.

The NFC Tag used are NFC NTAG203 Type 2, with 137 bytes of usable memory.

With this setup we seem to be able to read (and write) only the first 16 pages of the NFC tag, the first 4 pages seem to be reserved, so it seem that the usable pages range from 4 to 15 (zero-based page number).

So it seem that the memory effectively accessible with a RFID ISO 14443-A Mifare Ultralight reader amount to 4*12 bytes = 48 Bytes.

We programmed the NFC tag with a Samsung Galaxy S4, then we read it with a PC+RFID reader, then we wrote some data on one page of the nfc tag with the RFID reader, then we re-read the NFC tag with the Galaxy S4. Everything worked without issue.

I don't know how NFC Tag delimit the string/data, but the Galaxy S4 knew that there were just X bytes of data on the NFC tag. So, if you plan to write the NFC tag with a RFID reader/writer, and the read it back with a smartphone, then you need to work out the data format standard used to define the kind of data, the string termination/size, and this kind of things.

I would like to keep clear that I don't know if reading an NFC Tag with a Mifare Ultralight RFID reader is a supported feature/standard: I just tried, and it worked.

Update

About the RFID Reader

I've been asked to add more details about the dirty experiment we did:
The RFID Reader we use is a RFID Reader/Writer BMU-01 built by Nexus Technologies

From the Italian version of the product page, you can download the driver and the SDK.

To do our dirty experiment, we used the ICTransfer.exe utility from the SDK: its a tiny software that you can use to test reading/writing from all the standard supported by the RFID Reader/Writer.

We configured the ICTransfer.exe to use the card type ISO 14443-A \ Mifare-Ultralight.

Once you have the RFID reader hooked up to the PC, and the driver installed, you should be able to start the ICTransfer.exe utility, then connect it to the RFID reader (Menu\Set(P)\PortSet then Menu\Set(P)\Connect), then you can try to read/write / NFC tag

The BMU-01 is a short distance reader, so it will detect the NFC Tag to a maximum distance of some centimeters (3/4 cm).

So we used the SDK utility to do our NFC read/write test. Clearly it's possible to use the sample and the documentation in the SDK to create a custom software to do the same.

About the NFC Tag

To do our test, we used some NFC Tag NTAG203 Type 2, I bought them here on Ebay. But there are a lot of reseller...
I'm not very expert about NFC Tag, anyway, I can tell you that some NFC tag is compatible with all smartphone, and some is not (as reported in the specification, so pay attention to the specs when you buy NFC tag).

Different type of NFC tag can hold different amount of information, the NFC Tag NTAG203 Type 2 we used have 137 bytes of usable memory when used with a proper NFC reader/writer (I used my Galaxy S4), but we have been able to access only 48 bytes of memory during our RFID Reader experiment.

About some of the different type of NCF Tag, I can copy/paste some information from the NCF Forum

NFC Forum Type 1 Tag Operation Specification Type 1 Tag is based on ISO/IEC 14443A. Tags are read and re-write capable; users can configure the tag to become read-only. Memory availability is 96 bytes and expandable to 2 kbyte.

NFC Forum Type 2 Tag Operation Specification Type 2 Tag is based on ISO/IEC 14443A. Tags are read and re-write capable; users can configure the tag to become read-only. Memory availability is 48 bytes and expandable to 2 kbyte.

NFC Forum Type 3 Tag Operation Specification Type 3 Tag is based on the Japanese Industrial Standard (JIS) X 6319-4, also known as FeliCa. Tags are pre-configured at manufacture to be either read and re-writable, or read-only. Memory availability is variable, theoretical memory limit is 1MByte per service.

NFC Forum Type 4 Tag Operation Specification 2.0 (November 2010) Type 4 Tag is fully compatible with the ISO/IEC 14443 standard series. Tags are pre-configured at manufacture to be either read and re-writable, or read-only. The memory availability is variable, up to 32 KBytes per service; the communication interface is either Type A or Type B compliant.

Another interesting website I've found with a lot of NFC information is here: http://rapidnfc.com/which_nfc_chip

There are two RFID ranges - the one you mentioned, at 13.5MHz, readable by NFC devices - and the other is 13.4KHz, which NFC cannot communicate with.

Two additional points to mention:

• RFID access systems most probably se only cards UID, not some data on the card. cards, is in 13.5MHZ range, are most probably of type4.
• Those stickers are most probably NFC tags type 2 I guess they have different uid length. most probably UID readers you have depend only on cards UIDs, and not some store content.

If you really want to replace cards, consult your provider to determine if there is an ability to reprogram the readers, or implement a programmable NFC reader on your own. I'd recommend an Arduino with NFC shield.