If you’ve ever tapped a card on a reader to enter an office, school, warehouse, hospital, or secure facility, you’ve used a prox card. Even though access control technology has evolved dramatically, prox cards still remain one of the most widely used and reliable authentication methods.
In this guide, we’ll explore what a prox card is, how prox cards work, why HID prox cards are considered the gold standard, and whether prox cards are still relevant today.
What Is a Prox Card?
A prox card, short for proximity card, is a contactless access card that operates on 125 kHz low-frequency RFID technology. Instead of swiping or inserting the card, the user simply brings it close to a reader. The system reads the card’s ID and unlocks the door if access is approved.
These cards are commonly used as employee ID badges, building entry cards, parking gate passes, and general access credentials in environments where simple, reliable, and low-maintenance security is required.
How Do Prox Cards Work?
Prox cards rely on radio-frequency identification. Although the technology may sound complicated, the working process is surprisingly simple.
First, the door reader emits a 125 kHz electromagnetic field. When a prox card comes near the reader, its internal antenna picks up this field. This powers the tiny chip inside the card, which then sends a unique identification number back to the reader. The access control system checks this number against its database, and if the user is authorized, the door unlocks.
Prox cards don’t contain a battery and require no physical contact, which is why they are long-lasting and extremely easy to use.
What Is an HID Prox Card?
When people discuss proximity cards, the name HID comes up almost instantly. HID is the most recognized brand in access control, and its prox cards are used in thousands of facilities worldwide.
Popular models like the HID 1326 ProxCard II and HID 1386 ISOProx II are known for their durability, consistent read range, and stable performance. HID prox cards are compatible with a large majority of 125 kHz readers, making them the preferred choice for organizations running legacy access control systems.
If a facility has older proximity readers installed, HID prox cards typically work right out of the box, which makes them incredibly convenient for large deployments.
Where Are Prox Cards Used?
Prox cards are ideal for environments where fast, simple, and contactless entry is important. You’ll find them in office buildings, educational campuses, hospitals, warehouses, industrial plants, retail stores, government facilities, and residential complexes. Many access control systems still rely heavily on 125 kHz technology, which keeps prox cards relevant and in demand.
Benefits of Prox Cards
Prox cards are popular for several reasons. They are simple to use—just hold the card near the reader and the system handles everything automatically. They are reliable and have decades of proven performance in real-world environments. Because they don’t require batteries or physical contact, they last a long time even with heavy daily usage.
One of the biggest advantages is compatibility. Most older access systems still operate on 125 kHz, and prox cards integrate with them without needing hardware upgrades. Additionally, prox cards are affordable, making them ideal for facilities that need to deploy hundreds or thousands of credentials at once.
Limitations of Prox Cards
While prox cards are convenient and widely supported, they do have limitations. They’re based on older technology and do not offer the advanced encryption found in modern smart cards or DESFire credentials. They cannot store complex data and should not be used in environments where high-security authentication is required. For highly sensitive facilities, upgrading to a smart card system is the better choice.
However, for general access control needs, prox cards are still more than sufficient.
Are Prox Cards Still Relevant in 2025?
Yes, prox cards are still widely used and continue to be a practical choice for many organizations. If your facility already uses 125 kHz readers, prox cards are cost-effective and reliable. They are perfect for everyday access control, especially where convenience and compatibility matter more than advanced security features.
If your security needs grow in the future, you can always upgrade to smart cards, MIFARE, DESFire, UHF, or mobile credentials.
FAQs
- What frequency do prox cards use?
Most prox cards operate at 125 kHz low-frequency RFID. - How close does a prox card need to be to the reader?
Usually one to three inches, depending on the card and reader. - Are HID prox cards better than generic ones?
HID cards are known for superior durability, consistent reads, and high-quality encoding. - Can prox cards be printed with custom designs?
Yes. ISO-style prox cards like HID 1386 can be fully printed and personalized. - When should I consider upgrading from prox cards?
If you need encryption, multi-layer security, or data-rich credentials, upgrading to a smart card or DESFire system is recommended.