A study by researchers at Dartmouth College has shown that placing a folded sheet of aluminum behind a Wi-Fi router can boost data speeds by more than 50%. The technique uses the principle of parabolic reflectors, which are curved surfaces that focus radio waves in a specific direction, similar to how car headlights concentrate light into a beam. This method requires no additional cost other than the time to fold the aluminum, making it a low-cost solution to improve Wi-Fi performance. The idea reportedly came from a Facebook tutorial, but it should not be confused with the popular myth of placing a coin on a router to improve signal strength. In 2017, a team from Dartmouth’s computer science department demonstrated that aluminum, when properly shaped, acts as a parabolic reflector, redirecting Wi-Fi signals toward a specific area. This approach allows users to create a custom reflector for around $35, which can outperform expensive directional antennas that cost thousands of dollars. Wi-Fi signals operate on the 2.4 and 5 GHz frequency bands, which are radio waves that bounce off the metal surface of the aluminum sheet and converge toward the targeted room. This helps reduce areas with weak or no signal, known as dead zones, while increasing data transfer speeds. Researchers, including Xia Zhou and teams from the University of Washington, UC Irvine, and Columbia University, developed a software tool called WiPrint to model room coverage and determine the best shape for the reflector. Their findings, presented at the ACM BuildSys 2017 conference, showed that this simple aluminum sheet can outperform more expensive directional antennas. In a test conducted by the website Pocket-lint in August 2025, placing a curved aluminum sheet behind a home router resulted in a 58% increase in download speed. The method involves cutting a 30 cm long sheet of aluminum, folding it into a C-shape with the shiny side facing inward, and placing it behind the router so that the opening faces the desired area. If the router has external antennas, the aluminum sheet should extend slightly beyond them. However, the effectiveness of this technique can vary based on factors like apartment layout, wall thickness, and the specific router model used.