ITOT tracks the S&P Total Market Index, covering essentially the entire investable US equity market from the largest mega-cap companies down to small-caps — roughly 2,500-3,500 companies in total. Like VTI, it is cap-weighted, meaning the largest companies dominate returns. The top holdings are identical to any US market-cap-weighted index — Apple, Microsoft, NVIDIA, Amazon and Alphabet — and these mega-caps drive the majority of day-to-day performance. At 0.03% expense ratio, ITOT is as cheap as equity investing gets. The small and mid-cap exposure beyond the S&P 500 adds some diversification relative to an S&P 500-only fund, though these smaller positions represent a modest fraction of total assets given the cap-weighting. For investors, ITOT and VTI are effectively interchangeable — both track the total US market at minimal cost, hold thousands of stocks and differ primarily in their index provider and minor composition details. The choice between them typically comes down to brokerage platform convenience and any small cost differences in trading.
