Summary
- I wrapped my router in foil; download dropped ~50% and ping rose ~67%, so the signal was partially blocked.
- Upload barely changed; upload speed seemed ISP-limited, not much affected by the foil.
- My foil ‘cage’ partly acted like a Faraday cage but had seams, no grounding; don’t cover routers — it poses a fire risk.
I grew up “borrowing” all sorts of things from the kitchen for my childhood arts and crafts — bare paper towel rolls, empty cereal boxes, and (to my parents’ dismay) yards upon yards of aluminum foil. I’d bend and mold the sheets into makeshift bowls and pretend metal walls. That crafty kid would be overjoyed to know she’d still be bending foil in the kitchen years later — only this time, as a real part of her job.
A few weeks ago, I conducted an experiment to see if putting aluminum foil behind my Wi-Firouter could boost the signal throughout my apartment. What started as a somewhat goofy idea ended up turning quite a few heads — and the results of the experiment raised more eyebrows than just mine: it actually worked. Well, sort of.
Now I’m back, armed with more aluminum and a new theory to test. What happens if I cover my router in foil? Could I actually foil my Wi-Fi signal? Pun absolutely intended. Here’s how it went.
Tin foil and aluminum foil aren’t the same — tin foil was used decades ago but has since been replaced by aluminum, which is cheaper and more flexible. The term stuck, though, so when I say “tin foil,” I mean aluminum foil.
Does covering your router with aluminum foil block Wi-Fi?
Back to the lab
Disclaimer: I do not recommend covering your router with any kind of material. Doing so can block airflow, trap heat, and potentially create a fire hazard. This experiment was conducted in a controlled environment under close supervision, with fire extinguishers on hand in case of emergency.
Like my original experiment, I tested my normal Wi-Fi signal with the NetSpot app, a basic Wi-Fi management and analysis tool. Afterward, I covered my router with an aluminum foil-lined frame and then tested the strength of the signal. My goal was to ultimately create a homemade Faraday cage, which is a sealed enclosure made of metal or another conductive material that blocks electromagnetic fields from entering or escaping.
The lack of pizzazz in my last experiment pushed me to get a little more creative this time — at least in the aesthetics department. So, I built my router its very own one-bed, no-bath tiny home out of cardboard, aluminum foil, and a dream.
I ran two tests: one without the aluminum house, and one with it. Both were conducted from the exact same spot using my iPhone 16 Pro, and the results were as follows:
Please note that NetSpot is a basic analysis app. There are far more advanced and pricey tools that can measure Wi-Fi performance more accurately. But for a fun, DIY experiment, NetSpot provided just the right amount of data.
What these numbers mean
And how well my aluminum ‘Faraday cage’ worked
There are three numbers present in this test, as well as my original experiment: Mbps Download, Mbps Upload, and Ping. Here’s what they mean:
Mbps Download (505.5 Mbps and 232.3 Mbps) is the download speed, or how fast data comes to your devices (like downloading a PDF, streaming videos, etc.). My speed dropped by more than half after I enclosed it in the aluminum housing, which was one of the two drastic differences I saw in this experiment. It’s likely because the foil was successfully blocking the Wi-Fi strength, even if only partially. As a result, less bandwidth was available.
Mbps Upload (23.2 Mbps and 23.7 Mbps) is the upload speed, or how fast data goes from you (like sending an email, posting to Instagram, etc.). With only 0.5 Mbps between the two trials, there was little to no difference here at all. It actually even ticked upwards, but we can safely attribute that to regular testing noise. I’ve tested the strength of my signal outside these fun aluminum foil experiments, and my Mbps Uploads typically range from around 22-25 Mbps on a daily basis. So, it’s likely that this measurement depends more on my ISP’s end than the kind of house my router lives in.
Ping (36 ms and 60 ms) is the response time, or how long data takes to go to a server and back. Unlike Mbps Download and Mbps Upload, you actually want the Ping time to be lower. When I added the aluminum foil housing, my latency increased by approximately 67%, which made my connection significantly laggier. Such a drastic change gives me reason to believe that the aluminum foil cage made my device work harder to maintain its link, which could have introduced the delay.
Overall, the ~50% hit my signal took to Download speed was the clearest indicator that the aluminum foil created a makeshift Faraday cage around my router. The ~67% ping increase was the second hint, because the response time jumping that much couldn’t be because my router was distracted by the decor of its new house. The lack of significant change to my upload time can most likely be attributed to my Internet Service Provider, and I don’t particularly have any bones to pick with Spectrum at my current speeds, aluminum present or not.
What is a Faraday cage?
And why my DIY experiment had flaws
A Faraday cage is a structure made of metal or another conductive material that blocks electrical fields and electromagnetic waves. Wi-Fi, radio signals, and even some kinds of lighting are kinds of electromagnetic waves, so they cannot pass through a Faraday cage. It’s named after Michael Faraday — the chemist and physicist who built the first one in 1836.
Faraday discovered that when waves encounter an electrical conductive surface, they induce currents in the metal that create their own electromagnetic field — which cancel out incoming waves. So, no external signals can find their way inside the cage. Basically, it’s electromagnetic insulation.
So, did I create an actual Faraday cage with my aluminum foil? No, because Faraday cages only work if the cage is completely continuous (no sizable gaps) and the signals blocked are proportional to the wavelength. For example, microwaves have a mesh screen in the door, which acts as a Faraday cage and prevents electromagnetic radiation from spilling into your kitchen. The mesh holes are intentionally smaller than the microwave’s electromagnetic wavelength, which is around 12cm. Therefore, the signals don’t escape.
You probably have experienced unintentional Faraday cages in your daily life. If you’ve ever stepped in an elevator or internal room in a building and lost signal for a few minutes, it was likely you were in an accidental Faraday cage of sorts.
So, yes, I did my best to completely enclose my router in aluminum foil, but without proper equipment or electrical tape, there was no confirming if every single seam was sealed — especially when it came to the hole in the back I made for the cables to come in. Plus, even full-blown cages don’t actually block everything unless they’re grounded. The four or five layers of aluminum foil felt pretty insulating to me, but there’s always a chance that during my crafty construction I missed a spot or two. Guess I’ll have to factor that in when I charge my router rent for its aluminum tiny-home.
