What Is iShares?

iShares is the ETF brand of BlackRock, not a separate company. BlackRock is the world's largest asset manager, running roughly $11 trillion to $12 trillion across all its strategies as of early 2026, and iShares is the line of exchange-traded funds it operates. When you buy an iShares fund like IVV or AGG, BlackRock is the manager behind it, the same way Vanguard manages VOO or State Street manages SPY.

The brand has a history worth knowing. iShares started at Barclays Global Investors, which built the lineup through the early 2000s. BlackRock acquired Barclays Global Investors in 2009, which is how iShares became part of BlackRock and how BlackRock became the dominant force in ETFs. That single acquisition is the reason the largest asset manager and the largest ETF provider are now the same firm.

iShares is the largest ETF provider in the world by assets under management, ahead of Vanguard and State Street's SPDR, the other two members of the “big three.” Beyond size, its real distinction is range: iShares offers the broadest lineup of any issuer, hundreds of ETFs covering core index exposure, every major sector, factor strategies, thematic bets, and a deep bond shelf. If a category has an ETF at all, iShares usually has one for it.

That breadth is the practical reason iShares shows up so often. Vanguard is the closest competitor by assets and matches iShares on the cost of core index funds, but Vanguard runs a narrower set of products. SPDR is known for a handful of giants like SPY and the sector SPDRs. iShares is the one provider you can build almost an entire portfolio inside, from a total-market core to a single-country or single-sector tilt, without leaving the brand.

The iShares Core lineup is the cheap, broad foundation of the brand, a small set of low-cost index ETFs designed to be portfolio building blocks rather than specialized bets. The headline Core funds are IVV (S&P 500) and ITOT (total US market) for the US core, IEFA (developed international) and IEMG (emerging markets) for abroad, and AGG (total US investment-grade bonds) for fixed income. Most sit around 0.03% to 0.09%, which puts them at the bottom of the cost range.

The point of the Core lineup is that you can assemble a complete, diversified portfolio from five or six cheap funds: a US core, an international fund or two, and a bond fund. IXUS is the Core total-international fund that pairs developed and emerging in one ticker if you prefer not to split IEFA and IEMG. On cost, these funds match Vanguard's VOO, VTI, VXUS, and BND closely, so the Core lineup is best understood as iShares' answer to Vanguard's low-cost building blocks rather than a unique advantage.

Where iShares pulls ahead is the rest of the catalog. It runs the widest selection of sector, factor, thematic, and bond ETFs of any provider, which is the real reason to reach for iShares over a leaner lineup. On the sector side, SOXX covers US semiconductors, IGV covers software, and ITA covers aerospace and defense, alongside iShares funds for every major industry group. Factor funds like the iShares Edge series tilt toward value, momentum, quality, and minimum volatility.

The bond shelf is just as deep. AGG holds the total US investment-grade market, while TLT, the iShares 20+ Year Treasury Bond ETF, is the best-known long-duration Treasury fund and a common way to express a view on long-term interest rates. There are iShares funds for short-term Treasuries, corporate credit, high yield, municipals, and inflation-protected bonds. For US small-caps, IWM tracks the Russell 2000, the most widely held small-cap ETF. No other provider matches this range across so many categories.

A handful of iShares funds anchor the lineup. IVV, the iShares Core S&P 500 ETF, tracks the roughly 500 largest US companies at about 0.03% and is one of the largest ETFs in the world, the direct rival to Vanguard's VOO and State Street's SPY. ITOT, the Core total-market fund, widens that to the entire US market, several thousand stocks, at the same cost. AGG, the Core total-bond fund, holds the total US investment-grade bond market and is the largest US bond ETF.

Beyond the Core trio, several specialized iShares funds are household names in their categories: TLT for long Treasuries, IWM for small-caps, DGRO (the iShares Core Dividend Growth ETF) for dividend growers, and sector funds like SOXX for chips and IGV for software. Together they show the pattern: cheap, broad Core funds for the foundation, and a deep bench of narrower funds for tilts.

iShares suits investors who want the widest ETF selection and the cheap Core building blocks in one place. If your plan is a simple, low-cost core, the iShares Core funds (IVV, ITOT, IEFA, IEMG, AGG) do the same job as Vanguard's equivalents at the same cost. If your plan also includes sector, factor, thematic, or specialized bond tilts, iShares is often the only provider with a fund for the exact slot you want, which is why many portfolios end up mixing iShares Core funds with iShares satellites.

The honest version: on the cheap broad-index funds, iShares does not beat Vanguard, it ties. The reason to favor iShares is breadth, not a cost edge on the core. For a fuller cross-provider view, see our best iShares ETFs guide, the matching what is Vanguard explainer, and the best ETF in every category roundup.

Expense ratios are approximate as of early 2026; verify the current figure on the iShares site. The table is a representative slice, not the full lineup: the Core funds (IVV, ITOT, AGG) sit at the cheap end, while sector funds like SOXX and small-cap funds like IWM cost more for narrower exposure. The S&P 500 fund here, IVV, is the direct counterpart to Vanguard's VOO covered in our best S&P 500 ETFs guide.

Knowing iShares has a fund for nearly every slot is the easy part. The harder step is deciding which iShares funds fit together given what you already own, because stacking IVV, a sector fund like SOXX, and a factor fund on top of each other can quietly double up the same mega-caps. That is where an AI assistant helps, because it can reason over your actual holdings rather than a generic list. The useful questions are specific: does this iShares fund overlap with what I hold, does it fill the slot I am trying to fill, and how has it done against the S&P 500.

That is where Walnut fits. It connects your existing brokerage through SnapTrade and lets you ask, in plain language through Claude, ChatGPT, or a built-in assistant, which iShares ETF fits a given role, how much a new fund overlaps with what you already own, and how each position is doing against the market. It is read-only by default, and you approve any trade. Walnut is not an investment adviser; it helps you see and act on your own portfolio rather than telling you what to buy.

iShares is BlackRock's ETF brand and the world's largest ETF provider by assets, with the broadest lineup of any issuer. Two things define it: the cheap iShares Core building blocks (IVV, ITOT, IEFA, IEMG, AGG) for a low-cost foundation, and the widest range of sector, factor, thematic, and bond ETFs anywhere, from SOXX and IWM to TLT. The honest framing: on the core funds iShares ties Vanguard on cost rather than beating it, so the breadth, not a price edge, is the reason to favor iShares.

From a connected account you can dig into any of these as an ETF, look at an individual stock one of them holds, or explore a theme you want exposure to. Holdings, expense ratios, and fund availability change over time; treat the specifics here as a starting point and confirm on the iShares site before deciding.