Overlay symbols normalized to % change from the 9:30 open so you can watch them move together — e.g. DIA (Dow) vs QQQ (Nasdaq-100). Drag the slider or hit Play to advance the session.
⚠ Free Yahoo data is 1-minute resolution — the smallest available. Sub-minute lead/lag (Dow ticking ahead of Nasdaq by seconds) is invisible at this scale; that needs a real-time tick feed. See the note below the chart.