Faraday Pouches Compared: What Actually Blocks 5G and RFID

Every day our devices talk to each other, to the cloud, and to the world. A Faraday pouch stops that chatter, giving you a pocket-sized shield against unwanted signals. The hard part is not buying one, it is telling a pouch that works from one that merely claims to.

What Makes a Faraday Pouch Work

Effectiveness comes down to three things, and a pouch that gets any one of them wrong fails regardless of how it is marketed:

• Frequency coverage. The pouch has to cover the bands you actually care about: cellular including the newer 5G bands, Wi-Fi at 2.4 and 5 GHz, Bluetooth, GPS, and the 13.56 MHz band used by RFID and NFC cards. A pouch that blocks Wi-Fi but not low-band cellular is not isolating the device.
• Attenuation. Shielding is measured in decibels, and the scale is logarithmic: every 10 dB is a tenfold reduction in signal power. That is why the gap between a 20 dB and a 60 dB pouch is not three times better, it is ten thousand times.
• Closure integrity. This is where most pouches fail in practice. The shield is only as good as its weakest seam, and a zipper that does not fully close, or a fold-over flap with too little overlap, leaks regardless of the material.

Materials typically combine a metallic foil or metallised film with a conductive fabric or mesh. The conductive layer does the shielding; the fabric keeps the pouch flexible and protects that layer from creasing, which matters because repeated folding is what eventually opens gaps.

Reading Manufacturer Specs Critically

An attenuation figure is only meaningful alongside the frequency it was measured at and the method used. A pouch quoting a single headline dB number without naming the band, or without saying whether the figure is a peak or an average across the range, has not told you very much. Independent testing on this category is scarce and vendor figures are rarely measured the same way twice, so treat any single number as a starting point rather than a guarantee.

This is also why there is no attenuation league table on this page. We have not bench-tested these products ourselves, and printing unverified vendor figures side by side implies a comparison that was never actually run.

Choosing by Use Case

Car key fob and relay-attack prevention

Relay attacks work by extending the range of a key fob so a device near your door can talk to your car. What matters is a fully sealed closure and coverage of the fob’s band, commonly 315 MHz or 433 MHz depending on region. A pouch sized so the fob sits well inside the shielded area, rather than pressed against a seam, matters more than a headline dB figure.

Smartphone privacy and travel

Here you need the whole spectrum covered at once, because a phone reaches for cellular, Wi-Fi, Bluetooth and GPS independently. Size matters too: a pouch that only just fits the phone holds the closure slightly open, which is the most common reason a pouch that worked last month does not now.

Cards and passports

Card skimming happens at 13.56 MHz, far lower than phone traffic, and a pouch optimised for cellular does not necessarily address it. If cards are the concern, look for an explicitly separate RFID compartment rather than assuming the main pocket covers it.

Budget versus premium

The cheapest pouches usually economise on the closure rather than the shielding material, which is the worse place to save. Buying at the low end, prioritise a generous overlapping flap or a double-fold closure over any claimed specification.

How to Verify a Pouch Yourself

You do not need lab equipment to catch an obviously failing pouch:

1. Call the phone while it is sealed inside. A working pouch sends the call straight to voicemail with no ring.
2. Check the signal reading before and after sealing. Phone signal strength is reported in negative dBm, so a weaker signal is a more negative number. Both iOS and Android can surface the raw dBm value in their field-test or network-status screens; watch it fall as the pouch closes.
3. Try to locate the phone with a find-my-device service. A sealed pouch should prevent a fresh location fix.
4. For a card, tap it against a contactless reader while it is inside. The reader should not register it at all.
5. Repeat the test every few months. Pouches degrade with creasing, and the failure is silent.

Common Pitfalls

• Assuming “RFID blocking” means signal blocking. RFID shielding addresses one narrow low-frequency band and says nothing about cellular or Wi-Fi.
• Overfilling the pouch, which stops the closure sealing properly.
• Buying on a single dB figure with no band or test method stated.
• Trusting a pouch indefinitely. Creases open gaps, and nothing warns you when it happens.

Faraday Pouches and Bags We Stock

These are the pouches and bags in our own catalogue. We have not bench-tested attenuation on them, so each page describes what the product is for rather than ranking it:

• Faraday Phone Pouch — single phone, everyday carry
• Car Key Fob Faraday Pouch — sized for fobs, the relay-attack use case
• GoDark Faraday Bag — larger, phone plus accessories
• GoDark Faraday Bag for Tablets — tablet sized
• GoDark Faraday Sleeve Case for Laptops — laptop sized

Key Takeaways

• Closure integrity fails more often than shielding material does, and it is the thing you can actually inspect before buying.
• A dB figure with no frequency and no test method attached is marketing, not a specification.
• RFID blocking and signal blocking are different claims about different frequencies.
• Test the pouch yourself, and retest periodically, before relying on it for anything that matters.

References

For the physics behind Faraday cages, see NIST’s Faraday cage overview.