ETF Research Tools — Screeners, Overlap, Holdings and Flows

People arrive at this section with one of four questions, and different tools answer each. If you are choosing between two index funds on the same benchmark, the expense ratio decides less than you think: compare total cost and tracking difference, which Trackinsight prints for free and ETF Research Center turns into a cost comparison. If you hold several funds and suspect they own the same stocks, you need holdings-based overlap. If you are a European buyer choosing UCITS funds, most of the US-built tools here do not list a single fund you can buy. And if you are watching where the money is going, flows are published daily and free in more places than the paywalls suggest.

• Total cost of two funds, not just the fee — ETF Research Center's TCO tool, Trackinsight for tracking difference.
• Overlap between two funds — ETF Research Center, free with a login.
• Overlap across a whole portfolio — ETF Insider, US-listed funds, $14 a month for full holdings.
• UCITS funds and European savings plans — justETF; Trackinsight for global listings side by side.
• Free screener and flows for US-listed funds — ETF.com.
• Daily flows with look-through behind them — ETF Action, from $29 a month.
• Ranking funds by trend and backtesting a rotation — ETFreplay.

Two jobs: ranking funds, and opening one up

The listing splits along the two things these tools do. A screener ranks funds against each other — on cost, size, performance, or for ETFreplay on relative strength — and is how you get from several thousand funds to five. Analytics opens a fund up: what it holds, how much of that another fund also holds, and money moving in and out. Most products lean one way. ETF.com, Trackinsight, justETF and ETFreplay are screeners first; ETF Research Center, ETF Insider and ETF Action are bought for what they show inside a fund.

What none of them sells is an answer to "which fund should I buy". ETF Research Center prints its own forward-return score and a five-step label from Speculative to Avoid on every fund page, and says how it is calculated; read it as one model's output, not as a fact about the fund.

The expense ratio is the smallest number on the bill

The expense ratio is the fee the issuer deducts, and the only cost most screeners sort by. It is not what you pay. Three other costs sit beside it and none is on the label.

The spread is paid on every purchase and sale. ETF Research Center averages each fund's bid/ask spread from NBBO observations over up to three months, and its TCO tool adds that and a round-trip commission to the fee over a holding period you choose — the comparison a long-term buyer of a thinly traded fund needs and a fee sort hides. ETF.com's fund pages print the daily spread and the maximum premium or discount to NAV.

Tracking difference is how far the fund actually trailed its index over a period, and it absorbs everything at once: the fee, withholding tax on the dividends the fund receives, securities-lending income, cash held between distributions. Trackinsight puts the one-year figure on every comparison page. On 7 October 2026, SPY against IVV read a TER of 0.0945% against 0.03%, and a one-year cumulative return difference of roughly −10 to −14 basis points for SPY against −3 to −4 for IVV. ETF.com's analysis of SPY names one reason: as a unit investment trust it cannot lend securities or reinvest dividends between distributions.

Withholding matters most when the fund and the shares it holds are in different countries, which is the normal case for a UCITS fund holding US stocks. No tool in this listing models it directly; it shows up only inside tracking difference, which is a reason to compare that rather than the fee.

Overlap is computed from holdings

Two funds with different names and different index providers can hold nearly the same thing. Overlap tools measure it, and they measure it from holdings, not from returns.

ETF Research Center does it pairwise and by weight: for each stock both funds hold it takes the smaller weight and sums them. SPY against QQQ came to 54% on 7 October 2026, across 85 shared names — 84% of QQQ's holdings were in SPY, only 17% of SPY's were in QQQ, which is why overlap is not symmetric and a single percentage needs reading carefully. The tool is equity-only. ETF Insider does the same job for a whole portfolio of ETFs, mutual funds and stocks at once, with a matrix of pairwise overlap and concentration by name, sector and country. Trackinsight lists holding overlap among its portfolio analytics, but the full version is in its institutional product.

The reverse lookup is just as useful: enter a stock and see which funds hold it. ETF Research Center, ETF.com and Trackinsight all offer one — Apple sat in 729 funds on ETF Research Center's count.

US-listed and UCITS are different universes

A fund tracking the S&P 500 exists several times over — SPY and VOO in New York, VUAA in Europe, others in Toronto, Sydney and Seoul — and a European investor generally buys the UCITS version. Coverage decides which tools are any use before features do.

US-listed only: ETF.com (5,871 funds in its screener on 7 October 2026), ETF Action, ETFreplay (about 1,500, and only funds past roughly $250 million in assets) and ETF Insider.

UCITS and US together: Trackinsight screens 15,875 funds across listing venues and adds French PEA eligibility and UK reporting status to its comparisons; ETF Research Center screens US, Canadian and UCITS universes.

UCITS only: justETF, whose domicile filter does not include the United States, and whose savings-plan filter has no US equivalent because the product does not exist there.

How old the holdings are

Prices and flows on these sites are daily. Holdings usually are not, and the gap is rarely printed where you would look for it.

On 7 October 2026 Trackinsight's SPY page carried prices and flows as of the previous close and holdings and sector weights stamped 31 August — while the same comparison page's text described those figures as "as of yesterday". ETF Insider takes most of its holdings from quarterly SEC filings, which the regulator allows up to 60 days after quarter end, so an overlap figure there can describe a portfolio as it stood months ago. ETF Research Center standardised performance as of 30 September and valued funds on the latest close.

Freshness is not the only data problem. ETF.com's screener, on FactSet data, listed IVV's expense ratio as 10% the same day — a fund that charges 0.03% — which would put it last in any cost sort. Issuers publish full holdings every business day on their own sites; for a decision that rests on one number, that is the copy to check. How to get ETF holdings as data covers the daily files and the SEC's quarterly ones.

What free covers, and where the paywall starts

More is free here than in most of the catalogue, because several of these sites are paid for by advertising and by the fund industry rather than by readers.

• Free with no account: ETF.com's screener, flows, comparisons and fund pages; Trackinsight's screener and two-fund comparisons; ETF Research Center's fund pages and the first five rows of its overlap and stock-locator results; ETFreplay's screener over the 100 largest funds.
• Free with a login: the full overlap and locator lists on ETF Research Center; flows, exposures and watchlists on Trackinsight; ETF.com's AI assistant.
• Where money starts: ETF Insider Pro at $14 a month or $99 a year for full holdings; justETF Premium from 9.90 € a month on annual billing, for portfolio tools rather than data; ETF Research Center at $29 a month for fundamentals and full holdings; ETF Action at $29 with Excel capped at 50 rows; ETFreplay at $29.99 a month or $199.90 a year.
• Sales calls: Trackinsight Enterprise and ETF Insider Enterprise publish no price.

The free sites carry advertising and sponsored content beside the data — ETF.com prints press releases under a fund's news, ETF Action runs sponsored model marketplaces, Trackinsight labels sponsored articles. None of that changes a number, but it is the price of the free tier.