next.js/packages/next/src/next-devtools/dev-overlay/icons/fullscreen.tsx

export function FullScreenIcon(props: React.SVGProps<SVGSVGElement>) {
  return (
    <svg
      xmlns="http://www.w3.org/2000/svg"
      width="16"
      height="16"
      viewBox="0 0 16 16"
      fill="none"
      {...props}
    >
      <path
        d="M15 14C15 14.5523 14.5523 15 14 15H10V13.5H13.5V10H15V14ZM2.5 13.499H6V14.999H2C1.44772 14.999 1 14.5513 1 13.999V9.99902H2.5V13.499ZM6 2.5H2.5V6H1V2C1 1.44772 1.44772 1 2 1H6V2.5ZM14 1C14.5523 1 15 1.44772 15 2V6H13.5V2.5H10V1H14Z"
        fill="currentColor"
      />
    </svg>
  )
}