How to Research an ETF Before You Buy (2026)

Federico Kunze Küllmer is the founder of Moneda, one of the tools compared here.

Short answer: Before you buy an ETF, find out four things. What it holds, what it costs each year, how closely it follows the index it copies, and how it fits with what you already own. You can get most of this from the fund's own fact sheet and prospectus. An AI research tool can pull it together faster, as long as it shows you where each number came from and you check the important ones yourself.

An ETF (exchange-traded fund) is a basket of investments you can buy and sell on a stock exchange like a single share. One ETF might hold the 500 largest US companies. Another might hold only gold, or only small Japanese banks. The name on the label often tells you less than you think, so it is worth a few minutes of checking before you put money in.

This guide walks through that check in eight steps. Each step has questions you can type into an AI, plus the things you should confirm yourself.

Step 1: Work out what the ETF is trying to do

Every ETF has a stated objective. Most try to track an index, which is a rule-based list of investments such as the S&P 500. Some are actively managed, which means a person or team picks the holdings and tries to beat a benchmark.

Start by finding the objective in one sentence. If you cannot explain it in plain words, you are not ready to buy it.

Questions to ask an AI:

• "What index does this ETF track, and how is that index built?"
• "Is this ETF passive or actively managed?"
• "Explain this fund's strategy as if I have never invested before."

What to verify yourself: read the objective on the issuer's fact sheet or in the prospectus, the legal document every fund must publish. The marketing page and the prospectus should say the same thing.

Step 2: Look at what it actually holds

The holdings are what you are really buying. A "technology" ETF might be 40% in three companies. A "global" fund might be mostly US shares.

Check three things:

1. Top 10 holdings and the share of the fund they make up. If the top 10 are more than half the fund, a few companies drive your returns.
2. Sector and country split. Does it match what the name suggests?
3. Number of holdings. Thirty holdings and three thousand holdings behave very differently.

Questions to ask an AI:

• "List the top 10 holdings of this ETF and what percentage each one is."
• "How concentrated is this fund compared with a broad market index fund?"
• "Which sectors and countries does this ETF have the most exposure to?"

What to verify yourself: holdings change. Check the date on any holdings list, and compare it with the issuer's latest published list.

Step 3: Find the full cost

The headline cost is the expense ratio, the yearly fee taken from the fund's assets. An expense ratio of 0.20% means about €2 a year for every €1,000 you hold. You never get a bill. It is quietly taken out of the fund's value.

That is not the only cost. You may also pay:

• The bid-ask spread: the gap between the price buyers pay and sellers get. Small, heavily traded ETFs can have wide spreads.
• Trading commissions, depending on your app or broker.
• Currency conversion, if you buy a US-listed ETF with euros.

Questions to ask an AI:

• "What is this ETF's expense ratio, and how does it compare with similar funds?"
• "How much would I pay in fees over 10 years on €5,000 at this expense ratio?"
• "Is this ETF traded enough that the spread should be small?"

What to verify yourself: confirm the expense ratio on the issuer's page or prospectus. Then check your own app's fee page for commissions and currency costs.

Step 4: Check how well it tracks its index

An index fund should follow its index closely. The gap between the two is called tracking difference. A fund that trails its index by much more than its expense ratio is losing money somewhere, often through trading costs, cash drag or sampling.

Questions to ask an AI:

• "How has this ETF performed against its index over the past 5 years, after fees?"
• "Why might this fund's returns differ from its index?"

What to verify yourself: compare the fund's published returns with the index returns over the same periods. Use periods of at least a few years. One good month says very little.

Step 5: Understand the risks

Every ETF can lose value. The question is how much, and in what kind of market.

Look at:

• Past drawdowns: the largest fall from a peak. How did the fund, or its index, do in 2008, 2020 and 2022?
• Volatility: how much the price moves around from day to day.
• Structure risk: some ETFs use borrowed money (leveraged ETFs) or derivatives. These can behave very differently from what you expect, especially over longer periods.
• Commodity exposure: an oil or gold ETF may hold futures contracts rather than the metal or barrel itself, which changes how it tracks the spot price.

Questions to ask an AI:

• "How did this ETF's index perform in 2008, 2020 and 2022?"
• "Is this a leveraged or inverse ETF? What does that mean for someone holding it for years?"
• "Give me the bull case and the bear case for this fund."

What to verify yourself: read the risk section of the prospectus. It is dull reading. It is also where the fund lists what can go wrong.

Step 6: Check size, age and issuer

Very small or very new funds can be closed down by the issuer. That is not a disaster, since you normally get your money back at the fund's value, but it can mean an unplanned sale and possibly a tax bill.

Questions to ask an AI:

• "How large is this ETF in assets, and when did it launch?"
• "Who issues this fund, and how many other ETFs do they run?"

What to verify yourself: fund size and launch date are on the fact sheet.

Step 7: See how it fits with what you already own

Two ETFs with different names can hold many of the same companies. If you already own a broad US index fund, a US large-cap growth ETF may add more of the same.

Questions to ask an AI:

• "How much do these two ETFs overlap?"
• "If I add this fund to my portfolio, how does my exposure to technology change?"
• "Compare my portfolio with gold and with a world index over the past 10 years."

What to verify yourself: look at the combined top holdings. If the same names keep appearing, you are less diversified than you think.

Step 8: Read the primary sources

AI summaries save time. They are not a replacement for the documents. For a US-listed ETF, the key ones are:

• Fact sheet: a one or two page summary from the issuer.
• Prospectus and summary prospectus: objective, fees, risks and how the fund works.
• Annual and semi-annual reports: what the fund held and what it cost to run.

US fund filings are on the SEC's EDGAR system, which lets you search filings by fund name, ticker or filing type.

A quick checklist

Using an AI to research ETFs

General AI assistants such as ChatGPT, Claude or Gemini can explain an ETF in plain English. The risk is that they sometimes state numbers without a source, or use figures that are out of date. Whatever tool you use, ask it where each number comes from, and check the ones that matter against the issuer's documents.

Moneda is built to do the research and the investing in the same place. For ETFs that includes gold, silver and oil through ETFs, researched before you buy. Moneda AI, the agent inside the Moneda app, is built on Numa 1, Moneda's financial AI engine. It researches stocks, ETFs, a few commodities through ETFs (gold, silver, oil) and crypto, from company filings and live market data. It works figures out from the data and shows the source behind each one. It gives you both sides of the story, the bull case and the bear case. It can build an illustrative portfolio from a goal you describe, stress-test it against 2008, 2020 and 2022, and benchmark it against gold, an index or any fund. It also tells you when something changes, sends daily briefings on your portfolio and the market, and has a screener for finding ETFs and stocks that match an idea you describe in plain words.

In Moneda's own tests in October 2026, the agent scored 97.9% on groundedness and 92% on claim verifiability. These are Moneda's own tests, not independent audits.

If you want to act on your research, you can buy US-listed ETFs, including fractional shares, in the same app. Every trade is approved by you with your passkey (face or fingerprint). The agent never tells you to buy or sell. If you prefer to work in Claude or ChatGPT, Moneda MCP connects them to your Moneda account with the permissions you choose.

Where it falls short: Moneda covers US-listed shares and ETFs only, so no European-listed ETFs.

Moneda Standard is free; Premium starts at €9.99 a month and Ultra at €19.99 a month, with more AI usage.

FAQ

What is the most important thing to check in an ETF?

What it holds. The name and the marketing tell you the idea. The holdings tell you what you are actually buying.

Is a lower expense ratio always better?

Usually, for funds that track the same index. A cheaper fund that tracks badly or trades with wide spreads can still cost you more overall, so look at tracking and spreads too.

Can I trust an AI's answer about an ETF?

Use it as a starting point. Ask for the source of every number, and check the key figures, such as fees and top holdings, against the issuer's fact sheet or prospectus.

What is the difference between an ETF and a mutual fund?

Both pool money into a basket of investments. An ETF trades on an exchange during the day like a share. A traditional mutual fund is usually bought and sold once a day at a price set after the market closes.

Are commodity ETFs the same as owning the commodity?

Not always. Some hold the physical metal. Others hold futures contracts, which can make their returns differ from the spot price over time. The prospectus says which.

How many ETFs do I need?

There is no fixed number. Many people start with one or two broad funds. Adding more only helps if the new fund holds something different from what you already own.

This guide is for information only and is not investment advice.