Does Aluminum Foil Block GPS Signal?

How GPS Systems Work (And Why Blocking Is Hard)

GPS tracking works by receiving radio signals from GPS satellites and processing them inside a GPS receiver within the tracking device. Blocking GPS isn’t about stopping one signal. Signal blocking requires preventing enough satellite communication that the receiver can’t calculate a position.

GPS receivers use trilateration, measuring how long each satellite signal takes to arrive. Those timing differences allow the device to calculate location, speed, and altitude. Better satellite visibility improves accuracy and makes interference harder to maintain.

From real-world installs I’ve done on car trackers and fleet vehicles, these factors matter most:

• GPS signals are weak electromagnetic waves, but they come from multiple satellites at once
• GPS receivers calculate location using timing data from several satellites, not just one
• Most trackers rely on four or more satellites to maintain accurate positioning
• If even one usable signal gets through, the tracking system can often recover

This explains why GPS tracking devices often drops in underground garages or metal-heavy areas, then reconnects quickly once the vehicle moves. I’ve seen trackers regain a location fix within seconds after returning to open space.

Aluminum foil enters the discussion because it can interfere with radio signals. The issue is density and coverage. Thin or imperfect shielding doesn’t block enough satellite communication to keep a GPS device offline for long.

In practical terms, blocking GPS tracking means cutting off satellite access consistently and that’s far more difficult than it sounds.

How Aluminum Foil Interferes With GPS Signals

Aluminum foil interferes with GPS signals because it’s a conductive material. When a GPS signal or an electromagnetic wave hits the foil, electrical currents move across the metal’s surface. Those currents reflect the signal away instead of letting it reach the GPS receiver.

From real testing, this is what actually determines the outcome:

1. A GPS signal reaches the metal: GPS signals are electromagnetic waves. When one hits aluminum foil, it interacts with the metal’s conductive surface.

2. The foil induces an electrical current: That incoming electromagnetic wave causes electrons in the foil to move, creating an electrical current across the metal.

3. An opposing electromagnetic field forms: The moving current generates its own electromagnetic field that opposes the incoming GPS signal.

4. The signal is reflected away: Instead of passing through to the GPS receiver, the signal is reflected outward, reducing or blocking reception.

5. The foil acts as a barrier: When the GPS device is fully enclosed, the foil limits radio signals from reaching the receiver.

6. This is known as signal shielding (Faraday cage effect): Wrapping a GPS device in aluminum foil creates a basic Faraday cage, disrupting GPS signal reception without actively transmitting interference.

7. Coverage determines effectiveness: Any gap, tear, or movement in the foil allows GPS signals to leak through, restoring tracking.

This is signal shielding, not signal jamming. Shielding stops GPS signals from reaching the device, while jamming actively interferes with GPS satellites, which aluminum foil doesn’t do. 

Because foil is thin and flexible, it rarely stays sealed for long. Once coverage shifts or opens up, GPS tracking usually comes right back.

Faraday Cages: What They Are and Why Foil Gets Compared to Them

A Faraday cage is named after Michael Faraday, an English scientist who figured out in the 1830s that conductive materials can block electromagnetic fields. When an electromagnetic wave hits a conductive surface, the charge spreads across the outside instead of passing through. Anything inside stays shielded.

That principle is still used today. True Faraday cages show up in places where blocking radio signals really plays a key role:

• MRI rooms, where stray electromagnetic interference would ruin imaging
• Radio studios that need clean signals
• Military and scientific equipment testing
• Sensitive electronics that can’t tolerate interference

I’ve been inside a few of these rooms. They’re not subtle. Thick walls, sealed seams, no gaps anywhere. That is the key difference.

When people talk about aluminum foil blocking GPS tracking, they’re really talking about a very crude Faraday cage. But foil bends, tears, and shifts. One small opening, and GPS receivers start hearing satellites again.

So yes, foil acts like a Faraday cage in theory. In practice, it’s more like trying to soundproof a room with a blanket. You might reduce the noise, but don’t expect silence.

If you want a detailed technical breakdown, this explainer does a solid job: https://science.howstuffworks.com/faraday-cage.htm

What GPS Signals Can and Cannot Penetrate

GPS tracking works by sending radio signals from GPS satellites down to a GPS device, such as a phone or a car tracker. The GPS receiver inside the device measures how long each signal takes to arrive, then uses that timing to calculate location, speed, and altitude.

I’ve seen people assume GPS signals behave the same around everything. They don’t.

Some materials let radio signals pass through with little resistance, while others weaken or block them entirely. Signal frequency and material density determine whether a GPS device keeps a connection or drops offline.

Below is a practical breakdown of which materials GPS signals can penetrate and which ones tend to block or interfere with them.

Whether GPS signals get through depends on signal frequency and material type. Because GPS uses radio signals, materials like plastic and glass allow them to pass with little resistance. Metals behave differently. They reflect or block signals, which keeps them from reaching the GPS device.

Aluminum foil sits in the middle. It can interfere with GPS tracking in some situations, but it’s inconsistent. Foil may weaken signals briefly, then fail once conditions change.

Aluminum Foil vs GPS Jamming: Two Very Different Things

People often lump these together, but they work in completely different ways.

Aluminum foil is shielding. Aluminum shielding blocks GPS signals from reaching the device by acting as a physical barrier. Nothing is transmitted and disrupted. If the coverage breaks or the device moves, GPS tracking usually comes back.

GPS jamming is active interference. A jammer sends out radio noise to overpower signals from GPS satellites. Jamming doesn’t just affect one tracker, it can disrupt nearby GPS systems as well.

From what I’ve seen in the field, this difference matters for two reasons:

• Shielding causes temporary, localized signal loss
• Jamming creates widespread interference and serious safety risks

Aluminum foil can only interfere passively. GPS jammers and GPS blockers actively disrupt electromagnetic waves and using them is illegal.

If you’re curious about how GPS jamming actually works, this guide breaks down the risks, legal consequences, and real-world impact: How To Make A Homemade GPS Jammer.

Why GPS Jammers Are Illegal

GPS jammers are illegal because they disrupt critical navigation and communication systems, not just individual tracking devices. They interfere with GPS signals used by aviation, emergency services, and public infrastructure, creating serious safety risks.

Jamming GPS signals is illegal, creates serious safety risks, and can lead to heavy fines or criminal charges. I’ve seen firsthand how much damage GPS jammers can cause, and it goes well beyond one vehicle losing tracking.

“A New Jersey truck driver, Gary Bojczak, was fined nearly $32,000 after using a GPS jammer in his work truck. The device didn’t just block a tracker, it also interfered with nearby airport navigation systems, creating a serious safety risk for pilots and ground crews.

The Federal Communications Commission (FCC) tracked the interference, confiscated the jammer, and made it clear that GPS jamming can lead to criminal charges, not just fines.”

GPS jammers don’t affect only the person using them. They disrupt GPS systems around them, including emergency services, aviation, and infrastructure. This is why the law is strict.

Final Thoughts From the Field

After working with GPS tracking systems for more than 15 years, I’ll tell you this straight: aluminum foil isn’t a reliable way to block GPS tracking. Foil can interfere under the right conditions, but it doesn’t hold up once real-world factors come into play.

Foil bends and shifts. Gaps open up. And GPS receivers are built to keep trying.

I’ve watched trackers drop offline in garages, warehouses, and metal-heavy environments then reconnect almost immediately once the vehicle moves. That’s not a failure. That’s how GPS systems are designed to work.

The confusion usually comes from mixing up shielding and jamming. Shielding blocks signals temporarily if coverage is perfect. Jamming actively disrupts GPS systems and crosses into illegal territory fast. There’s a reason the law treats those two very differently.

If your goal is understanding privacy, tracking behavior, or why a device lost signal, the science counts more than shortcuts. 

Bottom line: aluminum foil may interfere for a moment, but it doesn’t defeat GPS tracking. In real-world conditions, consistency beats tricks every time and GPS systems are built with that in mind.

Author Disclosure

Written by Ryan Horban, GPS tracking specialist with 15+ years of hands-on experience testing vehicle trackers, car trackers, and fleet GPS systems in real-world conditions.

Over the years, I’ve tested GPS trackers in real-world conditions like cars, trucks, and fleet vehicles, specifically to see how GPS signals react to metal, enclosed spaces, and movement. The goal is always simple: help you understand how GPS systems actually work, avoid unreliable assumptions, and make informed decisions without risking illegal signal jamming or safety issues.

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