What it is

A Faraday pouch is a passive enclosure made of conductive fabric that attenuates radio signals entering or leaving the device inside it. While the pouch is fully sealed, a phone, tag, key fob or hardware wallet cannot reach a cell tower, Wi-Fi access point, Bluetooth peer, GNSS satellite or RFID reader. There is no battery, firmware or logic — the physics do the work, and only while the seam is closed.

Honest positioning

This is a containment tool with a narrow, well-defined job: stop RF for a bounded window of time. Independent testing (Matt Blaze, using a Rohde & Schwarz PR100 in an RF chamber) measured 89–110 dB of attenuation across 1–6 GHz on good commercial pouches, with roughly ±10 dB uncertainty and noticeable drop-off when a closure was imperfect. Cheap "metallic-look" pouches can deliver almost nothing. A pouch is only as good as its weakest seam.

What it does not do

A Faraday pouch does not change anything the device knows or stores, and it does not touch the network's record of you. The baseband, IMEI/IMSI, your SIM, your accounts and your past location history are untouched; the moment you reopen the pouch, the device re-registers and tracking resumes. It also cannot stop a phone from recording audio or sensor data internally for later upload. Treat it as airplane-mode-you-can-physically-trust for short periods — not as anonymity, and not as a defense against seizure or forensic extraction.

Usage guide

Setup and first-use verification

A Faraday pouch needs no configuration, but you should verify it works before relying on it — attenuation depends entirely on the seam, and units vary.

Quick acceptance test (do this on day one)

1. Call test. Put the powered-on phone inside, seal fully, and call it from another phone. It should go straight to voicemail / unreachable. Reopen — it should reconnect within seconds.
2. Bluetooth/Wi-Fi test. Pair the phone to a Bluetooth speaker or keep an active Wi-Fi stream; sealing the pouch should drop the link. SLNT documents exactly this four-part method (call / Wi-Fi / Bluetooth / RF).
3. Location test. Use a friend's "Find My"/locator on the device; the last fix should freeze while sealed.

If any signal survives a *full, correct* seal, the pouch (or its closure) is inadequate — return it.

Daily use

• Seal completely, every time. For roll-tops, roll the documented number of folds and secure both clasps; for hook-and-loop, press the full overlap. Most real-world failures are an incompletely closed pouch, not bad fabric.
• Don't overstuff. Cables or a second device can hold the seam open a few millimeters — enough to leak.
• Power down for the strongest guarantee. A sealed pouch blocks RF, but a powered phone still records sensors and burns battery hunting for signal at full transmit power (older phones especially). If you only need to stop emission, sealing is enough; if you want to stop *collection*, power off first.
• Mind heat and battery. A live phone transmitting at max inside a sealed pouch runs warmer and drains faster. Don't leave a live device bagged for long periods.

Hardening

• Combine, don't substitute. Enable airplane mode *and* bag the device. On GrapheneOS, airplane mode fully disables the cellular radio; the pouch is your physical fallback if a setting fails or an app re-enables a radio.
• Address the device, not just the RF. The pouch does nothing about EXIF metadata, account linkage, or on-device logging. Pair it with disciplined OS/app hygiene.
• Inspect the seam regularly. Conductive thread and plated fabric degrade with flexing, abrasion and washing. A frayed or creased closure loses attenuation silently.
• Avoid washing. Most conductive fabrics lose shielding when laundered; follow the maker's care instructions or replace.

Pitfalls

• "It looks metallic so it works." Decorative fabrics can give <10 dB. Only a sealed, tested, multi-layer conductive pouch is meaningful.
• Trusting it against seizure. Forensic-grade Faraday bags exist specifically to keep a *seized* phone live and isolated for extraction with Cellebrite/GrayKey — the bag protects the investigator's evidence, not your secrets. A pouch is not a defense against physical custody.
• mmWave gap. High-band 5G (>20 GHz) is often untested; don't assume coverage there.
• Forgetting the re-registration moment. The instant you reopen the pouch, the device rejoins the network and location resumes. The protected window ends the moment the seam opens.

How to verify integrity over time

Re-run the call/Bluetooth/RF acceptance test monthly and after any drop, wash, or visible wear. For a quantitative check, a cheap RF detector or SDR placed inside vs. outside a sealed pouch will show whether a known transmitter still leaks — the same principle Matt Blaze used in his phone-sized Faraday bag tests. If attenuation has dropped, retire the pouch.