Same idea, two wrappers
An index fund follows a passive strategy designed to match the return of an index before fees. It can be set up as a traditional mutual fund or as an exchange-traded fund (ETF).[1] An ETF trades on a stock exchange during the day, like a share.[2] A traditional index fund is bought from and sold back to the fund company once a day.
| ETF | Index mutual fund | |
|---|---|---|
| How you buy | On an exchange, at a live price during market hours | Once a day, at that day's fund price |
| Cost to buy | Brokerage commission and a bid-ask spread can apply | Often no transaction fee |
| Smallest purchase | One share, unless your broker offers fractions or a savings plan | Often a small fixed amount |
| Monthly saving | Depends on the broker | Usually simple to automate |
What matters more than the wrapper
- Which index it tracks. A broad global index spreads the risk over many companies and countries.
- The annual fee. Morningstar's research finds that the fee is the most reliable predictor of a fund's future returns.[3]
- How closely it follows the index after costs (tracking difference).
Which is easier depends on where you live
What your platform offers cheaply matters most. In Sweden, index mutual funds with automatic monthly saving are common. In Germany, ETF savings plans are widely offered. In the UK, both are easy to hold in an ISA. Pick the one you can buy regularly without transaction costs eating into small deposits.
Common questions
Is an ETF riskier than an index fund?
Not because it is an ETF. The risk comes from what the fund holds. An ETF and a mutual fund tracking the same index carry very similar market risk. Leveraged and inverse ETFs are a different matter and are not suited to long-term saving.
Can I own both?
Yes. Many investors hold an index mutual fund for monthly saving and an ETF for a market their fund platform does not cover.
Sources & further reading
We cite independent authorities so you can verify everything yourself. Last reviewed 15 Sept 2026.