The key difference between 125kHz and 13.56MHz access cards is security. Most 125kHz (low-frequency, LF) proximity cards broadcast a fixed number without encryption and can be copied cheaply. 13.56MHz (high-frequency, HF) cards support mutual authentication, encrypted memory, several applications on one card and phone NFC compatibility. For a new access control installation, choose a current, encrypted 13.56MHz card family.
Key takeaways
- A 125kHz proximity card broadcasts its fixed number unencrypted and can be copied in seconds with cheap devices.
- A 13.56MHz card supports encrypted memory and mutual authentication, yet can still be imitated if the reader only reads its serial number.
- The NFC used for phone-based entry runs at 13.56MHz; 125kHz readers cannot talk to phones.
- According to HID Global's 2024 research, one in three companies still supports 125kHz proximity cards.
- Dual-frequency readers allow a phased migration: critical zones such as server rooms first, then general areas.
How do 125kHz and 13.56MHz cards work?
Two cards can look identical yet do different jobs. Hand someone a plain white PVC card and they cannot tell its frequency by looking at it. They hold it to the reader, hear the beep and the door opens; the frequency difference lies in what happens between the RFID (radio-frequency identification) reader and the card in that half-second.
A 125kHz proximity card draws power from the reader's field and transmits the ID number written into it at the factory. The reader passes that number to the system, which checks whether it is authorised. There is no "prove it" step: anyone who knows the number can be that card.
A 13.56MHz smart card can carry a microprocessor or secure memory. The reader asks it an encrypted question to confirm it is genuine, and the card can only produce the right answer with the secret key it holds. That turns the card into more than a number: canteen meal balances, zone permissions or another application's data can sit in separate, protected areas. Asset and stock tracking, by contrast, uses UHF RFID for bulk reads at a distance; see RFID inventory and asset tracking.
As of 2026, many organisations still run 125kHz cards on a system installed years ago. Running legacy cards is common and not a failing in itself, but you need to know what it does and does not protect. We explain how to replace such a system without disrupting doors, cards or payroll in replacing a legacy access control system.
125kHz vs 13.56MHz access cards: comparison table
| Criterion | 125kHz (LF, proximity) | 13.56MHz (HF) |
|---|---|---|
| What is read | Usually just a fixed ID number | ID plus encrypted memory areas |
| Authentication | None; the number is sent in the clear | Mutual authentication (depends on card family) |
| Cloning risk | High; can be copied with cheap tools | Low with current encrypted cards |
| Multiple applications | Not in practice | Possible in separate sectors or applications |
| Phone (NFC) compatibility | No | NFC works on the same frequency |
| Relevant standards | Mostly manufacturer-specific formats | ISO/IEC 14443 (e.g. MIFARE), ISO/IEC 15693 |
| Card and reader cost | Generally lower | Generally somewhat higher |
One point in the 125kHz vs 13.56MHz comparison deserves emphasis: 13.56MHz on its own is not a guarantee of security. The encryption on some older 13.56MHz card families was broken years ago, and many installations configure the reader to read only the card's unique identifier (UID, its serial number), never touching the encrypted memory. In that case a 13.56MHz card is almost as easy to imitate as a 125kHz one. The right question is not "which frequency?" but "how does the reader verify the card?"
Do reading range and environment differ between the two frequencies?
In access control, both 125kHz and 13.56MHz technologies work at short range, with the card held up to the reader; at the door, users notice no difference in speed. The real differences show up on site. When readers are mounted near metal door frames, turnstile housings or electrical panels, reader position and antenna should be tested at either frequency; that is more about installation quality than card choice.
How people carry their cards also affects reading. Reading behaviour changes if staff keep the card in a phone case, carry two different cards in the same wallet or wear it on a lanyard. A pilot on a few doors with real users therefore gives more reliable results than catalogue figures. The same pilot is a good chance to see how long card printing and distribution take and how lost-card reports will be handled.
What is the risk of staying on 125kHz cards?
A cloneable 125kHz card is a gap that even the guard at the gate cannot see: a copy produces exactly the same log entry as the original. Anyone reviewing the access logs sees an "authorised" person going in. It is also one of the first things testers try in a penetration test that covers physical security: copying the card of an employee they pass in the corridor in a few seconds. How to spot a copy made by card cloning in the logs and shut it down is covered in access card cloning risk.
The 125kHz card cloning risk is neither theoretical nor niche. In HID Global's survey of more than 1,200 security professionals, one in three companies still supported 125kHz low-frequency proximity cards, and nearly 30% still had systems using magnetic stripe cards (HID 2024 State of Physical Access Control Report, as reported by CampusIDNews).
The same research found that 39% of organisations now actively use mobile identities. (HID Global, 2024 State of Physical Access Control)
The move to mobile credentials affects the frequency decision directly: phone near-field communication (NFC) operates at 13.56MHz and cannot talk to 125kHz readers. An organisation investing in 125kHz today may have to replace its readers again when it wants phone-based entry or QR visitor access tomorrow. Phone-based entry methods are covered in detail in our mobile access control guide.
The market is heading the same way. MarketsandMarkets forecasts that the global access control market will grow from USD 10.62 billion in 2025 to USD 15.80 billion by 2030 (MarketsandMarkets, Access Control Market – Global Forecast to 2030), with cloud platforms and Internet of Things (IoT) based systems among the drivers, both of which are built on current, encrypted credential technology.
How do you choose the right access card? A five-step framework
- Define risk by zone. A car park entrance and a server room do not need the same level of assurance. High-risk zones require encrypted authentication; in low-risk areas convenience can take priority. For card + PIN or biometric options, see our fingerprint vs card vs face recognition comparison.
- Take stock of what you have. How many cards are in circulation, which reader models are installed, and how does each reader verify each card? The problem is often not the card but a reader set up to read only the serial number.
- Choose the card family together with key management. Current AES (Advanced Encryption Standard) encrypted card families offer strong protection, but decide up front who holds the encryption keys, how they are loaded during card printing and what happens if they are lost.
- Plan a phased migration. Dual-frequency readers and dual-technology cards let you migrate without replacing every employee's card overnight. Start with critical zones, then general areas.
- Remember the personal data. Once a card number is linked to an employee, it is personal data. How it is stored, who can see it and how long it is kept all form part of KVKK compliance under Türkiye's personal data protection law.
Card choice also shapes total system cost; we break the cost items down in access control system cost, and cover the basics in our card access control system guide.
How Digital Bridge handles card migration
Because Digital Bridge handles hardware and software in the same team, it treats a migration from 125kHz to 13.56MHz cards as a single piece of work:
- Site inventory and risk map. We inspect your readers, card types and zones on site and work out which door needs which level of assurance. Technical feasibility for hardware is free of charge.
- Hardware design and installation. Under our card access control service we install 125kHz and 13.56MHz readers, locks and door controllers, turnstiles and barriers, and design a layout that reads both technologies during the transition.
- High-security points. Where a card alone is not enough, we combine it with a second factor such as fingerprint access.
- Security and compliance. We address card and key management through our cyber security consultancy, and the storage of card data through data protection compliance.
- Integration. We connect access data to your HR, payroll or ERP systems through system integrations.
SmartPass: 13.56MHz cards for staff and visitors
SmartPass, the Smart360 family product developed by Digital Bridge, works with 13.56MHz MIFARE and NFC-readable cards: it reads only the card's ID number (UID) and writes nothing to the card. Staff carry permanent cards, and visitors receive a temporary card at entry, limited to the visit's access group and duration. Both are read by the same readers and follow the same permission rules, so the frequency decision and the visitor management decision are not made separately. Where there is no fixed door, an NFC-enabled Android phone (Android 9 or later) can act as a mobile terminal and read the same cards.
In SmartPass, card security continues into the database: card numbers are not stored: at the moment of reading, the device turns the number into a one-way hash using a key unique to the organisation, and the database holds only the hash and the last four digits. Even someone with database access cannot extract a list of card numbers. Once the retention period ends, the fields that link records to a person are deleted automatically every day; every change is kept in the audit log with its previous and new value, and viewing the audit log report requires a separate panel permission.
In a concrete scenario, a manufacturing site is moving from an old 125kHz system to SmartPass. It issues 13.56MHz cards first for critical zones such as the server room and warehouse. The warehouse team is placed in an access group, and the group is linked to the Warehouse zone with a weekly time profile that covers working hours. A rule changed in the panel applies at every door at once, and a refused read is logged with its reason, such as "no zone permission" or "outside permitted hours".
The same 13.56MHz card deducts a meal in the canteen and creates an attendance record at the door, with no separate personnel attendance (PDKS) device needed. To buy SmartPass, fill in the SmartPass request form with your number of access points and people; hardware and installation are defined during the site survey.
Next step
If you do not know what frequency the access card at your door uses, or how the reader verifies it, that is the first thing to find out. Send us one card and the reader model, and we will assess the current set-up and the options for a phased migration together. For a proposal or site visit, use our contact page.
For the physical layer that sits behind the reader, see our guide to types of turnstiles; every related article is in our access control and attendance hub.