How a Car Key Fob Works: Complete Guide 2025

Car key fobs are now a standard feature for most modern vehicles. In fact, around 80% of new cars in the UK come with a keyless entry system, which means the traditional metal car key is being replaced by digital fobs.

In this Keytek Auto Locksmith guide, we explain everything you need to know about car key fobs—from how they work, how they differ from standard keys, and how secure they really are.

What is a Car Key Fob?

A car key fob is a small remote-control device that allows drivers to unlock, lock, and even start their car without physically inserting a key.

Inside a fob is a short-range radio transmitter that sends a unique code to the car’s receiver. When you press the button on the fob, the car recognises the code and responds by locking or unlocking the doors.

Some advanced fobs can also:

• Open and close windows

• Open the boot

• Arm or disarm the car alarm

• Start the car with a push-button ignition

How Do Fob Car Keys Work?

Car key fobs rely on Radio Frequency Identification (RFID) technology. Here’s the process:

1. Each fob has a unique digital code paired with your car.

2. When you press the button, the fob transmits this code via radio frequency.

3. The car’s onboard system verifies the code.

4. If the code matches, the car unlocks, locks, or starts.

   
   

To improve security, most modern fobs use a rolling code system—a new code is generated every time the fob is used. This prevents thieves from recording and replaying old signals.

Car Key Fob vs. Standard Car Key

The biggest difference between a fob key and a traditional key is convenience and functionality.

Feature	Standard Car Key	Car Key Fob
Unlock doors	Insert into lock manually	Press a button remotely
Start car	Insert into ignition	Push-button start (with fob inside)
Alarm control	Usually a separate system	Integrated into fob
Extra function	None	Boot release, window control, remote start (varies by model)

How to Unlock a Car with a Key Fob

Using a key fob is simple:

1. Stand near your vehicle.

2. Press the unlock button (or hold the fob close to the car’s reader if it has proximity entry).

3. The car will receive the code and unlock the doors.

For push-to-start cars, you usually just need the fob inside the vehicle—no need to press anything on the fob.

Are Car Key Fobs Secure?

Car key fobs generally offer better security than standard keys because of their encrypted codes and rolling security systems. However, they are not completely risk-free.

The biggest threat is relay theft, where thieves use devices to capture the signal from a fob inside your home and transmit it to your car, tricking it into unlocking.

How to Protect Your Car Key Fob from Theft

• Store your fob in a Faraday pouch (blocks signals)

• Keep your fob away from doors and windows

• Switch off the fob’s wireless signal if your model allows

• Consider using a steering wheel lock as an extra deterrent