If you’re deciding between FSKAX or FZROX, you’re already looking at two popular Fidelity index funds designed to give investors broad exposure to the U.S. stock market. At first glance, they can seem almost identical—and in many ways, they are. Both invest primarily in U.S. stocks, both are highly diversified, and both are designed for long-term investors rather than frequent traders.
The biggest difference is the expense ratio and the index each fund tracks. FSKAX charges a tiny 0.015% expense ratio, while FZROX has a 0.00% expense ratio. FSKAX also holds more securities and tracks the Dow Jones U.S. Total Stock Market Index, while FZROX follows Fidelity’s U.S. Total Investable Market Index.
Although they look/sound similar, they serve completely different purposes. In reality, their purposes overlap heavily. The important question is which fund’s structure fits your account, investing strategy, and long-term preferences
What Is FSKAX?
Meaning and Usage
FSKAX is the ticker symbol for the Fidelity Total Market Index Fund. It is an index mutual fund designed to provide broad exposure to the U.S. equity market.
The fund tracks the Dow Jones U.S. Total Stock Market Index, which represents a broad selection of U.S. companies across different market capitalizations. Fidelity reports that FSKAX had 3,778 holdings as of June 30, 2026.
For example:
- “I use FSKAX as a core U.S. stock holding.”
- “FSKAX gives me exposure to large, mid, and smaller U.S. companies.”
- “I’m comparing FSKAX with another total-market fund.”
Expense Ratio
As of April 29, 2026, FSKAX has an expense ratio of 0.015%. That works out to approximately $0.15 per year for every $1,000 invested, before considering investment performance.
That fee is already extremely low. Therefore, although FZROX has a zero expense ratio, the difference is tiny in dollar terms.
Diversification and Holdings
FSKAX provides exposure to thousands of companies. Its largest holdings currently include companies such as NVIDIA, Apple, Microsoft, Amazon, Alphabet, Broadcom, and Tesla.
The fund is overwhelmingly U.S.-focused, with 99.45% listed under United States exposure as of June 30, 2026.
History
FSKAX traces its fund history back to 1997, giving it a considerably longer operating history than FZROX. Its current share class began in 2011.
That longer history can be useful when evaluating how a fund has behaved through different market environments.
What Is FZROX?
Meaning and Usage
FZROX is the ticker symbol for the Fidelity ZERO Total Market Index Fund.
The fund is designed to provide broad exposure to U.S. companies and uses Fidelity’s U.S. Total Investable Market Index as its benchmark. Fidelity reports 2,665 holdings as of June 30, 2026.
For example:
- “FZROX is my low-cost total-market fund.”
- “I like FZROX because it has a zero expense ratio.”
- “FZROX is designed for broad U.S. stock exposure.”
Zero Expense Ratio
The most obvious attraction of FZROX is right in its name.
As of December 30, 2025, Fidelity reports a 0.00% expense ratio for FZROX.
That means the fund does not charge the standard management expense that many index funds do.
However, a 0.00% expense ratio does not mean investing is completely free of every possible cost. Taxes, account-specific costs, bid-ask spreads on other investments, and other factors can still matter depending on how and where you invest.
Diversification and Holdings
FZROX is also highly diversified. Its largest positions are very similar to those of FSKAX, with NVIDIA, Apple, Microsoft, Amazon, Alphabet, Broadcom, and other major companies among its largest holdings.
As of June 30, 2026, Fidelity listed FZROX at approximately 99.41% United States exposure.
History
FZROX was launched in 2018, making it considerably newer than FSKAX.
That doesn’t make FZROX inherently worse. It simply means it has a shorter live track record.
Key Differences Between FSKAX or FZROX
The differences between FSKAX or FZROX are relatively small for a long-term investor, but they are still worth understanding.
- FSKAX charges 0.015%.
- FZROX charges 0.00%.
- FSKAX tracks the Dow Jones U.S. Total Stock Market Index.
- FZROX tracks the Fidelity U.S. Total Investable Market Index.
- FSKAX currently holds more securities than FZROX.
- Both funds are heavily concentrated in U.S. equities.
- Both provide broad exposure to large, mid, and smaller companies.
- Their largest holdings are remarkably similar.
- FSKAX has a much longer history.
- FZROX has the advantage of a zero expense ratio.
- Both are designed primarily as long-term U.S. equity investments.
| Feature | FSKAX | FZROX |
|---|---|---|
| Fund | Fidelity Total Market Index Fund | Fidelity ZERO Total Market Index Fund |
| Expense ratio | 0.015% | 0.00% |
| Benchmark | Dow Jones U.S. Total Stock Market Index | Fidelity U.S. Total Investable Market Index |
| Holdings | 3,778 | 2,665 |
| Fund inception | 1997 | 2018 |
| U.S. exposure | About 99.45% | About 99.41% |
| Investment type | U.S. total-market index mutual fund | U.S. total-market index mutual fund |
| Major holdings | Very similar | Very similar |
| Main attraction | Established broad-market fund | Zero expense ratio |
| Best for | Investors wanting a traditional total-market index fund | Investors prioritizing zero fund expenses |
Current fund data above is from Fidelity’s published information as of June–August 2026.
Real-Life Conversation Examples
Example 1: The Zero-Fee Argument
Emma: “Why would I choose FSKAX when FZROX has a 0.00% expense ratio?”
Noah: “That’s a reasonable question. The fee difference is extremely small, so you should also compare the funds’ indexes, holdings, account considerations, and tax characteristics.”
🎯 Lesson: A zero expense ratio is attractive, but it isn’t the only factor that matters.
Example 2: Similar Investments
Liam: “Do I really get something completely different with FZROX?”
Sara: “Not really. Both funds give you broad U.S. stock-market exposure, and their largest holdings are very similar.”
🎯 Lesson: FSKAX and FZROX have substantial overlap.
Example 3: Fund History
Jack: “Which one has been around longer?”
Mia: “FSKAX. Its fund history goes back to 1997, while FZROX began in 2018.”
🎯 Lesson: FSKAX has the longer live operating history.
Example 4: Building a Portfolio
Alex: “If I buy FZROX, do I automatically have international stocks?”
Ben: “No. FZROX is primarily a U.S. equity fund.”
🎯 Lesson: Neither fund should be confused with a global or international stock fund.
When to Use FSKAX or FZROX
Choose FSKAX If You Prefer a Long-Established Fund
FSKAX can make sense if you value:
- A long fund history
- Broad U.S. market exposure
- The Dow Jones U.S. Total Stock Market Index
- A very low expense ratio
- Thousands of holdings
- A traditional Fidelity total-market index fund
Its 0.015% expense ratio is already extremely low, so the difference between FSKAX and a zero-fee fund may be less important than it first appears.
Consider FZROX If Zero Expenses Matter to You
FZROX may appeal if you prioritize:
- A 0.00% expense ratio
- Broad U.S. equity exposure
- Fidelity’s ZERO fund lineup
- A simple long-term index strategy
- Keeping recurring fund expenses as low as possible
Its current expense ratio is genuinely zero according to Fidelity’s published data.
What About Performance?
Recent performance should not be interpreted as proof that one fund will permanently outperform the other.
As of July 31, 2026, Fidelity reported one-year returns of 19.68% for FSKAX and 19.87% for FZROX, with five-year annualized returns of 11.76% and 11.98%, respectively.
Those differences are relatively small and can change over time.
The important point is that past performance does not guarantee future results.
What About Taxes?
Tax treatment can depend heavily on whether you’re investing through a taxable brokerage account, IRA, 401(k), or another type of account.
In a taxable account, investors may care about distributions and tax efficiency in addition to expense ratios. In tax-advantaged accounts, some of those concerns can work differently.
So if you’re choosing FSKAX or FZROX for a taxable account, it’s worth checking recent distribution history and considering your own tax situation rather than choosing solely based on the word “ZERO.”
What About International Diversification?
This is an important point.
Neither FSKAX nor FZROX is a complete global portfolio. Both are overwhelmingly invested in U.S. companies.
If your goal is broad worldwide diversification, you would need to consider whether another fund or a separate international allocation belongs in your overall portfolio.
A Simple Memory Trick
Think of them this way:
FSKAX = established total-market fund with a tiny fee.
FZROX = total-market fund with a zero expense ratio.
Both can serve as a core U.S. stock allocation, but they are not literally identical funds.
Fun Facts or History
FZROX Was Created Much Later
FSKAX has roots going back to 1997, while FZROX launched in 2018. That makes FZROX a relatively young fund compared with FSKAX.
Their Largest Holdings Look Very Similar
Despite using different indexes, the two funds currently have remarkably similar top holdings. NVIDIA and Apple, for example, occupy very similar portfolio weights in both funds.
That helps explain why their long-term performance can look quite similar even though the underlying index methodologies aren’t identical.
Conclusion
When comparing FSKAX or FZROX, you’re choosing between two highly similar Fidelity funds rather than two completely different investments. FSKAX tracks the Dow Jones U.S. Total Stock Market Index, has a long history, holds thousands of securities, and charges an exceptionally low 0.015% expense ratio. FZROX has a 0.00% expense ratio, follows Fidelity’s U.S. Total Investable Market Index, and also provides broad U.S. stock exposure.
For many long-term investors, either can work well as a U.S. total-market holding. The better choice depends on your account type, tax considerations, preferred index, and whether the zero-fee structure matters to you. Always consider your complete portfolio rather than evaluating either fund in isolation.