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RFID Tag (125kHz)

You might know RFID as the technology that Big Brother uses to track your every move. Quickly, don the tinfoil hats!!

Only kidding. RFID is useful for sensing and identifying tagged people and objects for access control, automation, and a whole range of different applications. This basic RFID tag works in the 125kHz RF range and comes with a unique 32-bit ID. It is not re-programmable. This blank, smooth, and mildly flexible RFID tag is ready for your logo (or hand-drawn scribble).

  • EM4001 ISO based RFID IC
  • 125kHz Carrier
  • 2kbps ASK
  • Manchester encoding
  • 32-bit unique ID
  • 64-bit data stream [Header+ID+Data+Parity]
  • 2.13 x 3.35 x 0.03" (54 x 85.5 x 0.8mm)


RFID Tag (125kHz) Product Help and Resources

SparkFun RFID Starter Kit Hookup Guide

May 5, 2015

Learn the basics of how to get started with the SparkFun RFID Starter Kit.


Looking for answers to technical questions?

We welcome your comments and suggestions below. However, if you are looking for solutions to technical questions please see our Technical Assistance page.

  • Does anyone know if is it possible to print a logo or photo on these with Zebra printers ?

  • YUSSSSS! Thank you for getting the old unbranded tags back!

  • I bought some of these cards ,and i see that they have a 10 byte unique id. But here it says that the have 32 bit ID. Can someone explain to me how can this happen?

    • This is quite a late reponse, but for anyone looking in the future: the data you see is a 10 DIGIT hexadecimal string, BUT only the last 8 digits are the ID. This is because the EM4100/4001 specification states that the RFID Tag has an 8 digit (hex) unique id, and a 2 digit (hex) facility ID. The 10 digits you see represent both the facility ID and the unique ID. One hex byte contains 4 binary bits, so the 8 digit ID is 32 binary bits (8*4).

      TL;DR: The 32bit spec refers only to the last 8 hexadecimal digits of the 10 digit string.

    • You're confusing yourself by calling the 32bit number a 10 byte number when it's actually a 10 digit number, not 10 byte. A 32bit number as stated by Applekid is from 0 - 4,295,967,295, which is the 10 DIGIT unique id.
      An example, an ID card can have a 10 digit id of 1004257542, which converted to 32bit, would be 111011110110111100000100000110 in binary.

    • A 32-bit number is ranged between 0 and 4294967295, inclusively. That 4 billion something number has 10 digits. Seems reasonable.

        • Stelios: No, its not a 10-byte id because its not in a hex / encoded format.
          NUMBER: 1236542458
          HEX: 49B423FA
          ENCODED: 31323336353432343538
          brrrrstickem: No, a 10-bit number would be in the range from 0-1023.
          It is a 32-bit number. Its put in a numberical form because of easy of use: "1236542458" is easier to read/fit on a card than "01001001101101000010001111111010"

    • i should be receiving mine pretty soon.
      however, i do want some explanations regarding this 32bits VS 10bytes thing

  • is it possible to change the id or to write info onto the card?

  • these cards come with a number of predefined id?

  • Is it possible to cut off any portion of the card? or does the entire card have to remain intact for it to work?

  • What are the various ways to add a logo and/or QR code to the cards?

  • Will a 13.56 MHz reader read 125 kHz tags such as this? Specifically with this 13.56 sparkfun shield.

  • how about UHF RFID sensors and tags???

  • Anyone know where I can get some key-fob type tags? I've got an arduino based RFID garage door opener and I need some more tags.. I'm having a reliability issue with the brand I was using, so I was hoping to try something new???

  • im new on rfid and i want to start some ID projects, i wanna know who is the way to write the tags? it is possible with the id 12/20 readers!?

  • Is there gonna be a replacement for this type of tag?

  • Dang, depreciated with no other tag? Any idea when you might have a replacement? I need a bunch and these guys are a lot cheaper than the capsule/buttons.

  • brrrrstickem:

    so that would be a 10 bit number
    No it's a 10 digit number.

  • When will you be getting more of these tags?

  • You should put white products on black backgrounds.

  • Very easy to use with arduino - I have written a tutorial that may be of interest here: http://wp.me/pQmjR-JL

  • I thought it was just a picture of a quarter, at first. I was quite confused.

  • doese this tag work with 125KHz RFID reader ID-12??????

  • These work great with the ID-20 reader and give 8cm of reading range! Any key fob with the same spec's (lots on ebay) will read just the same.
    These are the thin cards, just like credit card thickness. Looks like you could print on them if you had a big fancy card printer. Reads fine even through a wallet.

  • did u guys use these to print on?

  • Are there any key FOB versions of this that is compatible with the ID-20?

  • Decent cards. Works as advertised with ID-12 reader.

Customer Reviews

5 out of 5

Based on 1 ratings:

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Great tags

They are just the size of a credit card and fit perfectly in a wallet. They also work at a pretty decent range, and do their job well.