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Before you can reorder access cards, replace a lost fob, or add new users, you need to answer one basic question: Does your system run on 125 kHz or 13.56 MHz? The two frequencies use completely different radio technology. A card built for one will not be read by a reader built only for the other, no matter how similar the plastic looks.
This guide explains the difference between low frequency and high frequency RFID credentials, shows you several practical ways to tell which one you have, and covers when it makes sense to upgrade from prox to smart card.
Free samples are available so you can test compatibility before you buy. Request a free 125 kHz or 13.56 MHz sample card to test on your reader
Every access control credential contains a small chip and an antenna tuned to a specific frequency. The reader on the wall broadcasts at that frequency, powers the chip, and reads back its data. If the frequencies do not match, the reader simply never sees the card.
That is why frequency is the first thing to pin down. Once you know it, you can narrow down the format, the bit structure, and the form factor. If you skip it, you risk ordering a full box of credentials that will not work at a single door.
125 kHz credentials are what most people mean when they say "prox cards." This low frequency RFID technology has been the backbone of commercial access control for decades and is still installed in a huge share of buildings.
AuthorizID's 26-bit H10301 125 kHz proximity credentials work with the same 26-bit Wiegand readers that read HID 1326 and 1386 cards.
13.56 MHz credentials are usually called smart cards, and they are the same frequency used by NFC on phones. High frequency RFID chips can store more data, support mutual authentication between card and reader, and hold multiple applications on one card.
AuthorizID carries 13.56 MHz MIFARE and NFC smart cards and fobs, including MIFARE Classic 1K compatible printable CR80 cards, key fobs, and anti-metal adhesive tags, plus MIFARE Ultralight EV1 cards.
One caution: 13.56 MHz is a frequency, not a single technology. HID iCLASS, iCLASS SE, and Seos also run at 13.56 MHz, but they use HID's own secure data model. A generic MIFARE card will not replace an iCLASS or Seos credential, even though the frequency is the same. If your cards say "iCLASS" or "Seos," contact us before ordering so we can confirm what your readers will accept.
You rarely need special equipment to identify card frequency. Work through these checks in order, and one of them will usually give you a clear answer.
Look closely at both sides, including any small laser-engraved text near the edge.
A thick, rigid clamshell card (roughly 0.070" with a slot punch) is almost always a 125 kHz prox card. Thin, credit-card-thickness cards can be either frequency, so move on to the next check.
With a flashlight behind a thin white card, you can often see the antenna. A 125 kHz card usually has a small, dense coil made of many turns of fine wire. A 13.56 MHz card typically has a few turns of wire running around the outer edge of the card. Heavily printed cards may be too opaque for this to work.
The reader tells you what the system expects, which matters more than the card itself. Look for a model name on the front or a label on the back.
The card format setting in your panel or software often reveals the technology. A 26-bit H10301 format usually indicates prox, though some MIFARE readers are also configured to output a 26-bit or 32-bit Wiegand number. Your integrator or system administrator can confirm.
Still not sure? Email AuthorizID's Technical Support Team (support@authoriz-id.com) clear photos of the front and back of your card and your reader, including any model labels. Our U.S.-based team can usually identify the technology and recommend a compatible credential.
Knowing your frequency narrows the field, but it does not finish the job.
At 125 kHz, there are several different modulation families and bit formats. An HID prox reader will not read an EM 4200 card, and a 26-bit card will not work on a panel expecting a 35-bit or 37-bit format. If your system uses a brand-specific format such as AWID, Keri, or Kantech, browse our proprietary format credentials.
At 13.56 MHz, the reader must be set to read the right chip and the right data. Many MIFARE readers read the card serial number, which works well with compatible MIFARE Classic 1K cards. Readers configured to authenticate to encrypted sectors, or to read only secure HID credentials, may require specially programmed cards.
125 kHz prox is not obsolete. For many sites, it remains a practical, affordable choice. The case for upgrading depends on your risk, budget, and plans.
For higher-security upgrades, ask your integrator about chip choice. MIFARE DESFire EV2/EV3 with AES encryption is generally regarded as stronger than MIFARE Classic, which has known cryptographic weaknesses.
Most facilities do not switch frequencies overnight. A phased migration keeps doors working while cardholders move to the new technology.
The surest way to confirm a credential works with your system is to test one on your own reader. A free sample lets you verify frequency, format, and enrollment on a live door before you commit to a full order.
Ask us for a free prox or MIFARE sample credential to confirm your frequency
