You’re staring at your Fidelity dashboard. There’s a sea of ticker symbols, but one keeps popping up in every Reddit thread and "Boglehead" forum: the Fidelity Total Market Index Fund (FSKAX).
It looks perfect on paper. It's cheap. It's huge. It basically owns every public company in America. But here’s the thing—most people treat it like a "set it and forget it" button without actually knowing what’s under the hood. Or worse, they confuse it with the "ZERO" fee version and miss out on the subtle nuances that actually matter for your tax bill.
💡 You might also like: Mike Lilley Net Worth: What Most People Get Wrong About the Numbers
If you’re trying to build a portfolio that survives the next decade, you’ve gotta look past the 0.015% expense ratio.
The 3,800-Company Illusion
When you buy a total stock market index, you think you’re getting equal slices of everything from Apple to a tiny lemonade stand in Nebraska. Not quite.
FSKAX tracks the Dow Jones U.S. Total Stock Market Index. Because it's market-cap weighted, the "total" part is a bit of a stretch in terms of impact. As of early 2026, the top 10 holdings—names like NVIDIA, Apple, and Microsoft—make up roughly 35% of the entire fund.
It’s top-heavy. Really top-heavy.
💡 You might also like: What Really Happened With the Stock Market Today: Why the Sell-off Is Hitting Your Portfolio
If Big Tech sneezes, this fund catches a cold. You aren't just betting on the "market"; you are specifically betting on the continued dominance of American mega-cap growth. While the fund technically holds over 3,800 stocks, those bottom 2,000 companies are basically rounding errors in your portfolio.
FSKAX vs. FZROX: The "Free" Trap
Fidelity made waves a few years back with their ZERO funds. FZROX (Fidelity ZERO Total Market Index Fund) has an expense ratio of exactly 0.00%.
Zero. Zip. Nada.
Naturally, people flocked to it. Why pay 0.015% for FSKAX when you can pay nothing for FZROX? Honestly, for many, the "free" version is fine, but there are two "gotchas" that nobody talks about until it's too late.
- Portability is a Nightmare: You cannot move FZROX to another brokerage. If you ever decide you hate Fidelity and want to move to Vanguard or Schwab, you have to sell your FZROX shares. In a taxable brokerage account, that means a massive tax bill on your capital gains. FSKAX, however, is a standard mutual fund. You can usually move it "in-kind" without selling.
- The Sampling Strategy: FZROX holds about 1,000 fewer stocks than FSKAX. It uses a proprietary index to avoid paying licensing fees. Does it matter for performance? Historically, they track very closely, but FSKAX is the "truer" representation of the entire market.
If you’re investing inside a Roth IRA or 401(k), go ahead and use the zero-fee fund. Taxes don't matter there. But if you’re using a regular taxable account? Stick with FSKAX or an ETF like VTI. Seriously.
Why the Fidelity Total Stock Market Index Still Matters in 2026
Even with the rise of specialized AI ETFs and "active" index funds, the boring old total market index is still the king of the mountain.
Why? Because it’s efficient.
The turnover ratio is incredibly low—usually around 3%. That means the fund isn't constantly buying and selling, which keeps those pesky capital gains distributions to a minimum. In the world of investing, what you keep is more important than what you make.
Comparing the Giants: FSKAX vs. VTSAX
Vanguard’s VTSAX is the OG. It's the fund that started the revolution. But in 2026, FSKAX is actually winning the price war.
| Feature | Fidelity (FSKAX) | Vanguard (VTSAX) |
|---|---|---|
| Expense Ratio | 0.015% | 0.04% |
| Min. Investment | $0 | $3,000 |
| Holdings | ~3,800 | ~3,700 |
| Index Tracked | Dow Jones US Total Market | CRSP US Total Market |
Vanguard’s "Admiral Shares" still require a $3,000 minimum. Fidelity basically lets you start with the change found in your couch cushions.
For a young investor just starting out, that $0 minimum is a game-changer. You don't have to wait until you've saved up thousands; you can buy $10 worth of the entire US economy today.
The "Non-Diversified" Shift
Something weird happened in late 2025. Fidelity updated the diversification policy for FSKAX. It can now operate as "non-diversified" when necessary.
Don't panic. This doesn't mean the fund is suddenly risky.
It's a technicality because the biggest companies in the US (the Mag 7 types) have grown so large that they were bumping up against old regulatory limits for "diversified" funds. By changing the label, Fidelity ensures the fund can actually track the index accurately without being forced to sell its winners just to satisfy an old rule. It’s a sign of the times—the market is more concentrated than ever.
✨ Don't miss: Why Your 2026 Income Tax Calculator Results Might Actually Surprise You
Actionable Steps for Your Portfolio
Stop overthinking it. If you want the most reliable, "boring" path to wealth in a Fidelity account, here is the playbook:
- Check your account type. Use FZROX in your IRA if you want to save every penny. Use FSKAX in your taxable brokerage to maintain portability and avoid future tax traps.
- Ignore the daily noise. Total market funds are meant to be held for decades. The 17% returns we saw in 2025 were great, but don't expect that every year.
- Automate the Boring. Set up a recurring transfer. Since there’s no minimum, you can have $50 a week go straight into the total market.
- Mind the tilt. If you already own a lot of individual tech stocks, realize that FSKAX is already giving you massive exposure to those same companies. You might be "doubling down" more than you realize.
The Fidelity Total Stock Market Index isn't a get-rich-quick scheme. It’s a get-rich-eventually plan. By owning a piece of everything, you guarantee you’ll own the next big winner—you just have to be patient enough to let it grow.