FDRXX vs SPAXX (2026)
Nearly the same fund. Both are Fidelity government money-market funds, and their holdings and yields track each other closely. FDRXX carries the lower expense ratio (0.37% against SPAXX’s 0.42%), so it usually nets slightly more. The difference is how you hold them: SPAXX is on Fidelity’s published list of core position choices and fills automatically; FDRXX is not on that list, so you buy it as a position. For idle cash, SPAXX is simpler; for a larger balance you will manage, FDRXX nets a little more.
By Wealthy Pot · Last updated October 2026
| Feature | FDRXX | SPAXX |
|---|---|---|
| Provider | Fidelity | Fidelity |
| Wrapper | Money-market fund | Money-market fund |
| Holdings type | Government | Government |
| 7-day SEC yield | 3.55% (7-day yield, Sep 30, 2026, SEC filing) | 3.48% (7-day yield, Sep 30, 2026, SEC filing) |
| Share price | Stable $1.00 NAV (targeted, not guaranteed) | Stable $1.00 NAV (targeted, not guaranteed) |
| Expense ratio | 0.37% | 0.42% |
| Minimum | $0 | $0 |
| State tax | Partly state-tax-exempt (52.2% U.S. government obligations, 2025, below the CA/CT/NY threshold) | Partly state-tax-exempt (50.9% U.S. government obligations, 2025, below the CA/CT/NY threshold) |
| Auto-sweep? | Not on Fidelity's published core position list (SPAXX, FZFXX, FCASH); bought as a position | Yes, one of Fidelity's core position choices (the FDIC sweep is the other option in some accounts) |
| Best for | Fidelity customers who want a government money fund with a lower expense ratio than SPAXX | Fidelity customers who want their idle cash to earn a yield automatically |
Where FDRXX wins
- A Fidelity government money fund with a 0.37% expense ratio, below SPAXX's 0.42%
Where SPAXX wins
- The default Fidelity core/sweep position: idle cash earns automatically
- No minimum investment
- Government fund (holds government debt and repos), lower credit risk than prime
- Portion of income is state-tax-exempt
Which should you choose?
Nearly the same fund. Both are Fidelity government money-market funds, and their holdings and yields track each other closely. FDRXX carries the lower expense ratio (0.37% against SPAXX’s 0.42%), so it usually nets slightly more. The difference is how you hold them: SPAXX is on Fidelity’s published list of core position choices and fills automatically; FDRXX is not on that list, so you buy it as a position. For idle cash, SPAXX is simpler; for a larger balance you will manage, FDRXX nets a little more.
Compare these against every fund in our money-market fund comparison.
We summarize the funds' published facts, not user reviews. Yields are variable, change daily, and are re-checked against each fund's official page. Neither money-market funds nor ETFs are FDIC-insured, and an ETF's share price can fall as well as rise. Some outbound links may be affiliate links. That never affects our comparisons. Nothing here is financial advice.