how did will communicate through the lights

In Stranger Things , Will communicates through the Christmas lights because his presence in the Upside Down can subtly affect electricity in the real world, and Joyce builds a crude “interface” that turns those disturbances into letters and words.

In-universe explanation

• The Upside Down overlaps Hawkins like a dark, frozen copy, so Will is physically in another dimension but still roughly in the same place as his house. The show repeatedly links the Upside Down and psychic activity to electrical disturbances such as flickering lights and surges.

• When Joyce plugs in the Christmas lights, Will’s attempts to reach out cause certain bulbs to glow or flicker more intensely, letting him “push” on individual lights as a kind of primitive telegraph.

The alphabet wall trick

• Joyce paints the alphabet on the wall and hangs a light over each letter, turning the whole living room into a giant Ouija board that Will can tap by energizing specific bulbs. Each lit bulb corresponds to a letter, so Will can spell out short phrases like “RUN.”

• Inside the Upside Down, Hawkins is stuck at an earlier point in time, so the letters are not literally on Will’s wall; this is why many fans consider the scene a partial plot hole. The most common explanation is that Joyce shouts out letters as they flash, allowing Will to infer which cluster of light corresponds to which letter and continue “talking” to her.

How season 4 adds context

• Season 4 shows Nancy, Steve, Robin, and Eddie using light-based effects (lamps, flashlights, etc.) to signal to people in the real world, confirming that human presence in the Upside Down can create localized electrical anomalies on the other side.

• This retroactively suggests that Will is doing the same thing in season 1: he notices that his touch or proximity makes certain lights bloom with that warm, particulate glow, and he learns to use that effect intentionally to communicate.

Fan theories and unresolved bits

• Some viewers think Will’s connection to the Upside Down and to Vecna makes him especially “tuned” to this kind of energy, giving him more control over the lights than an ordinary person would have.

• Others argue that the show leaves the mechanics deliberately vague for emotional impact: the important thing is not a hard sci‑fi rule set, but the image of a desperate kid turning strands of cheap Christmas lights into a fragile, flickering lifeline to his mom.

TL;DR: Will can communicate through the lights because people in the Upside Down can disturb electricity in the normal world, and Joyce’s alphabet wall turns those disturbances into readable messages, even if a few details stay fuzzy or borderline plot‑hole territory.

Information gathered from public forums or data available on the internet and portrayed here.