Wealthy PotFZROX vs FXAIX: Fidelity's Zero-Fee Total Market vs the 500
FZROX and FXAIX are two of Fidelity's most popular index funds, and both are astonishingly cheap. But they are not the same fund at a different price, they own different things, and one of them comes with a string attached that matters the day you ever decide to leave Fidelity. This guide uses figures pulled straight from Fidelity's own fund pages.
The Short Answer
- Want the entire U.S. market (large, mid, and small caps) for literally zero fee, and you plan to stay at Fidelity? FZROX. It charges 0.00% and holds ~2,646 stocks.
- Want the S&P 500 specifically, a real portable index fund, or you might ever move brokers? FXAIX. Its 0.015% fee is almost nothing ($1.50 a year per $10,000), it tracks the actual S&P 500, and unlike FZROX it can be transferred to another broker without selling.
The decision is less about the fee (both are trivial) and more about what you want to own and whether you're locked in.
What Each One Owns
- FZROX is the Fidelity ZERO Total Market Index Fund. It tracks the Fidelity U.S. Total Investable Market Index, Fidelity's own proprietary index, and holds about 2,646 stocks spanning large, mid, and small caps, roughly the whole U.S. stock market. It launched in August 2018.
- FXAIX is the Fidelity 500 Index Fund. It tracks the S&P 500, about 508 holdings of large-cap U.S. companies, and it has been around since 1988 with a long track record.
So FZROX is a total-market fund and FXAIX is a large-cap fund. Historically the two move almost together, because large caps dominate the total market by weight, but FZROX adds the small and mid caps that the S&P 500 leaves out.
FZROX vs FXAIX Side by Side
| Feature | FZROX | FXAIX |
|---|---|---|
| Fund | Fidelity ZERO Total Market | Fidelity 500 Index |
| Expense ratio | 0.00% | 0.015% |
| Index tracked | Fidelity U.S. Total Investable Market (proprietary) | S&P 500 |
| What it covers | Entire U.S. market (large + mid + small) | Large-cap U.S. (S&P 500) |
| Number of holdings | ~2,646 | ~508 |
| Minimum investment | $0 | $0 |
| Inception | Aug 2, 2018 | Feb 17, 1988 |
| Avg annual return (NAV) | 14.39% since inception (2018) | 15.49% over 10 years |
| Transfer to another broker in-kind? | No | Yes |
Note the return rows cover different time periods and are not an apples-to-apples race, FZROX simply hasn't existed for ten years. Over any shared period the two are very close, with small differences driven by FZROX's small- and mid-cap sleeve and the slightly different indexes.
The Catch: You Can't Take FZROX With You
Here is the real deciding factor. The Fidelity ZERO funds, including FZROX, use Fidelity's own proprietary indexes and are only available at Fidelity. Per Fidelity's prospectus, they cannot be transferred in-kind to another brokerage. If you ever want to move to Vanguard, Schwab, or anywhere else, you'd have to sell FZROX first, which in a taxable account means realizing capital gains and a potential tax bill.
FXAIX, which tracks the standard S&P 500, doesn't have this problem, it can be moved to another broker in-kind. That makes the 0.015% fee look less like a cost and more like an insurance premium against being locked in.
Rule of thumb: the lock-in barely matters in an IRA (you can sell and rebuy with no tax), so FZROX shines there. In a taxable brokerage account, FXAIX's portability is worth far more than the tiny fee difference.
Which One Fits You
Choose FZROX if: you want the whole U.S. market including small and mid caps, you value paying literally 0.00%, and you're holding it in a Fidelity IRA (or you're confident you'll stay at Fidelity long-term). It's a fine, complete U.S. equity core.
Choose FXAIX if: you specifically want the S&P 500, you're investing in a taxable account, or you want the freedom to move brokers later. The 0.015% fee is negligible, and you get a real, portable, benchmark index fund with a decades-long record. If you'd rather hold the S&P 500 as an ETF you can also compare FXAIX vs VOO.
FAQ
Is FZROX better than FXAIX?
Neither is strictly better, they own different things. FZROX is a total-market fund at 0.00%; FXAIX is an S&P 500 fund at 0.015%. FZROX adds small and mid caps and is free but can't leave Fidelity; FXAIX tracks the actual S&P 500 and is portable. In a taxable account, FXAIX's portability usually wins; in a Fidelity IRA, FZROX's zero fee shines.
What is the difference between FZROX and FXAIX?
FZROX holds the entire U.S. market (~2,646 stocks, large/mid/small) via Fidelity's proprietary index at a 0.00% fee. FXAIX holds the S&P 500 (~508 large-cap stocks) at 0.015%. FZROX is broader and free; FXAIX is large-cap-only, tracks a standard benchmark, and is transferable to other brokers.
Can I transfer FZROX to another broker?
No. Fidelity ZERO funds like FZROX are proprietary to Fidelity and cannot be transferred in-kind. To move to another broker you'd have to sell, which can trigger capital-gains tax in a taxable account. FXAIX does not have this restriction.
Why does FXAIX charge a fee if FZROX is free?
FXAIX pays to license the S&P 500 index; the ZERO funds avoid that by using Fidelity's own indexes. At 0.015%, FXAIX costs about $1.50 per year per $10,000, in exchange you get a standard benchmark and portability.
Related comparisons: FNILX vs FXAIX · FXAIX vs VOO · SWPPX vs VOO · All ETF comparisons
Primary sources: expense ratios, indexes, holdings, and returns are from Fidelity's official fund pages for FZROX and FXAIX (FXAIX figures per its Jun 30, 2026 fact sheet; ZERO-fund fees as of Dec 30, 2025). The in-kind transfer restriction on Fidelity ZERO funds is per Fidelity's fund prospectus. For background on index investing, see the SEC's Investor.gov guide to mutual funds and ETFs.
This article is for educational purposes only and is not investment advice. Investing involves risk, including possible loss of principal, and past performance does not guarantee future results. Expense ratios and fund holdings change over time; confirm current figures on Fidelity's site before investing. Consult a qualified financial professional before making investment decisions.