GoogleAI: “According to special relativity, there is no valid reference frame at the speed of light because a reference frame with zero spatial width and zero time elapsing doesn’t exist. If there were a valid reference frame where light was at rest, the speed of light would be different in different reference frames. As a reference frame moves faster, its space contracts and its time slows down relative to a stationary observer.”

Based on: Why is time frozen from light’s perspective?