A Faraday bag is a signal-blocking pouch that prevents relay theft — a technique where thieves use an amplifier to extend your key fob's signal from inside your home, tricking your car into unlocking. The best Faraday fob pouches cost $8–$15 for a 2-pack on Amazon and take seconds to use. Our top pick is the CPWUFIYD 2-Pack (~$10) — compact, effective, and the best-reviewed option available.
⭐ Best Faraday Bags 2026
- Best overall (2-pack): CPWUFIYD Mini Faraday Fob Protector (~$10)
- Best for fob + phone: Wisdompro Faraday Bag (~$13)
- Best 2-pack with GPS blocking: Anti-GPS RFID Blocker 2-Pack (~$15)
- Budget pick: ONEVER Signal Blocking Bag (~$11)
How Does Relay Theft Work — and How Does a Faraday Bag Stop It?
Modern keyless entry cars constantly broadcast a low-power signal looking for your fob. When the fob is within range (typically 1–3 metres), the car unlocks. Relay theft exploits this by using two devices — one thief stands near your front door with an amplifier, the other stands at your car. The amplifier extends the fob's signal across 20–30 metres, fooling the car into thinking the fob is present.
A Faraday bag uses conductive metal mesh or carbon fibre to block all RF signals. Your fob inside a Faraday bag broadcasts nothing — there's no signal to amplify, and relay theft is impossible.
Top Faraday Bag Reviews
How to Test if Your Faraday Bag is Working
Put your fob in the bag and seal it
Make sure the bag is fully closed — any gap in the seal breaks the Faraday cage.
Walk to within 1 metre of your car
Stand close enough that your car would normally detect the fob.
Try to open the door
If the bag is working correctly, the car door will NOT open. The key fob signal is completely blocked.
Remove the fob from the bag
The car should now detect the fob and unlock normally.