FZROX vs FSKAX: Which Fidelity Total Market Fund in 2026?

Both funds aim to own the entire U.S. stock market. FSKAX (Fidelity Total Market Index Fund, launched 1997) tracks the Dow Jones U.S. Total Stock Market Index and holds about 3,750 stocks. FZROX (Fidelity ZERO Total Market Index Fund, launched 2018) tracks Fidelity's own U.S. Total Investable Market Index and holds about 2,600. Fidelity built the in-house index for FZROX so it would not have to pay index licensing fees, which is part of how it can charge nothing.

Over the five years ending September 2026, FZROX returned 12.79% a year and FSKAX 12.59%. Volatility was the same (about 16% a year). The extra stocks in FSKAX are tiny companies that make up a small slice of the market by weight, so they barely move the result.

The practical difference is where you can hold them. FZROX lives only in Fidelity accounts; if you transfer to another broker, you have to sell it first. FSKAX can usually be transferred, though other brokers may charge to buy more. Distributions also differ: FZROX pays once a year in December, while FSKAX has paid twice a year (April and December).

In a Fidelity IRA, Roth IRA, or HSA you plan to keep at Fidelity, FZROX is the natural pick. In a taxable account, the portability of FSKAX (or better yet, a total-market ETF like VTI or ITOT) protects you from being forced to sell and realize gains if you ever switch brokers. If your 401(k) only offers one of them, either is an excellent core holding.