Best Faraday bag car key signal blockers 2025
Which of these car key signal blockers is best at preventing relay theft?
Criminals no longer go equipped with a crowbar and screwdriver to steal your car. The modern generation of crooks use sophisticated technology to bypass security systems, exploiting weaknesses to drive them away without even needing to break a window.
The most common hi-tech method is called relay theft, which uses boosters to amplify the signal from a keyless remote control. It means that a key left inside your house or even in your pocket when you’re out and about can be used to open and start a car that is on your driveway or in a car park.
To avoid and prevent keyless car thefts, experts recommend keeping your keys inside a Faraday box or pouch, which blocks the signals. They vary in cost, size and quality, with some that are designed to fit in your pocket, while others are big enough to keep all the family’s keys in one place. We’ve been putting six contenders to the test.
How we tested them
We know that these pouches can degrade in everyday use, leading to cracks in the signal-proof material. To simulate hard daily usage, we put key-like 62g weights in the pouches and put them in a tumble dryer on a cool setting for 30 minutes. This represents five movements per day for a year.
Used - available now
2022 BMW
X1
58,784 milesAutomaticDiesel2.0L
Cash £16,903
2022 MG
HS
35,197 milesManualPetrol1.5L
Cash £13,903
2022 Fiat
500e
29,954 milesAutomaticElectric
Cash £11,500
2021 MG
MG 5 EV
35,501 milesAutomaticElectric
Cash £12,500We then put keys for a 2024 Vauxhall Astra and a 2015 Nissan X-Trail into the pouches and attempted to open the doors and start the cars, in addition to checking for Bluetooth leaks through the material with Apple AirPods.
Features such as key chains gained extra points and we also scored the pouches on value, bearing in mind that many of the products are supplied in twin packs.
Verdict
All of the blockers we tried would make it much more difficult for a thief to boost your key’s signal and use it to steal your car. But we would have expected them to prevent us opening and starting both models we tried, and some simply didn’t.
The Hilka did the job you’d expect at a great price, so takes the win. We loved the Disklabs KS1 but baulk at the price. Halfords Car Key Signal Blocker takes third place.
Hilka Pro-Craft Faraday Car Key Signal Blocker
- Price: Around £8.00 (two pack)
- Size: 14 x 9cm
- Rating: 5 stars
- Contact: screwfix.com
It might not have any fancy features, but the Hilka Pro-Craft Blocker is a no-nonsense pouch at a good price. Once we’d popped our keys into the rearmost of the two pockets and secured the flap with the full-width hook and fastener, there was no chance we were going to be able to open or start the cars. We couldn’t find any trace of a Bluetooth signal, either.
The Hilka is small enough to be kept in a drawer or handbag, and at £7.99 for a twin pack, it represent great value.
Disklabs KS1 Faraday Bag Signal Blocker
- Price: Around £25.00
- Size: 12 x 10cm
- Rating: 4 stars
- Contact: fonefunshop.com
As you might expect at the price (double that of our Best Buy), the Disklabs KS1 has a real high-quality look and feel.
It’s small, but the tough canvas pocket took our larger key and fob without an issue and totally blocked all signals once the large top had been folded over and fastened. There’s a tab sewn in to make it easy to hang on a hook or attach a ring with other keys. The KS1 would be our top choice if cost wasn’t a factor, but it’s simply too expensive to beat the bargain Hilka.
Halfords Car Key Signal Blocker
- Price: Around £6
- Size: 13 x 9cm
- Rating: 3.5 stars
- Contact: halfords.com
There’s nothing wrong with the Halfords blocker, because it is just about big enough for a larger fob and small bunch of keys. It blocked all the key signals, but did allow some Bluetooth through on the front panel, and it is difficult to seal completely when the pouch is full. There are no extra features, either, and rivals are better value.
Disklabs KSH KS3 Faraday Bag Signal Blocker
- Price: Around £38.00
- Size: 23 x 14cm
- Rating: 3.5 stars
- Contact: fonefunshop.com
The Disklabs KSH KS3 is called the Home Edition, because it uses the same technology and robust design as the smaller KS1, but in a pouch which is big enough to store multiple remotes. This could make it perfect for storing all your spare keys or keeping the family’s fobs together in one place. Unfortunately, the KSH’s cost is sizeable, too.
Honor Car Key Signal Blocker
- Price: Around £7.00 (2 pack)
- Size: 14 x 9cm
- Rating: 2.5 stars
- Contact: amazon.co.uk
The Honor key blocker looks stylish, with a carbon fibre-effect skin. It’s also big enough for most fobs and we like the chain and ring inside the pouch, which makes it easier to retrieve your keys. You can’t really argue with the value either, at £6.99 for a twin pack. But while the Honor made it impossible to open the cars’ doors, we were still able to start the Nissan with the key in the pouch.
Defender Signal Blocker
- Price: Around £7.00 (2 pack)
- Size: 18.6 x 11.5 cm
- Rating: 2 stars
- Contact: defendersecurityproducts.co.uk
We had high hopes for the Defender Signal blocker because it looks great value at £6.95 for two. The pouches are larger than most, too, meaning they will hold the biggest key fobs, and you might be able to squeeze a smartphone in at a push.
But after the endurance test we could open and start our Nissan easily with the keys carefully placed in the pouch; Bluetooth signals weren’t blocked either.
Now boost your car’s security even further by fitting one of the best dash cams...
