The following table describes the fees and expenses that you will incur if you buy, hold and sell shares of the Fund. The investment advisory agreement between BlackRock ETF Trust II (the “Trust”) and BlackRock Fund Advisors (“BFA”) (the “Investment Advisory Agreement”) provides that BFA will pay all operating expenses of the Fund, except the management fees, interest expenses, taxes, expenses incurred with respect to the acquisition and disposition of portfolio securities and the execution of portfolio transactions, including brokerage commissions (other than any commitment fee relating to a committed line of credit), distribution fees or expenses, litigation expenses and any extraordinary expenses.

You may also incur usual and customary brokerage commissions and other charges when buying or selling shares of the Fund, which are not reflected in the Example that follows:

Operating Expenses Caption [Text]

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Annual Fund Operating Expenses (ongoing expenses that you pay each year as a percentage of the value of your investments)

Fee Waiver or Reimbursement over Assets, Date of Termination

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June 30, 2024 June 30, 2026

Portfolio Turnover [Heading]

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Portfolio Turnover.

Portfolio Turnover [Text Block]

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The Fund may pay transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in the Annual Fund Operating Expenses or in the Example, affect the Fund’s performance. There has been no portfolio turnover because the Fund has not commenced operations as of the date of this prospectus (the “Prospectus”).

Expense Example [Heading]

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Example.

Expense Example Narrative [Text Block]

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This Example is intended to help you compare the cost of owning shares of the Fund with the cost of investing in other funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then sell all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions, your costs would be:

Strategy [Heading]

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Principal Investment Strategies

Strategy Narrative [Text Block]

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The Fund normally invests at least 80% of its assets in floating rate loans and investments that are the economic equivalent of floating rate loans, which effectively enables the Fund to achieve a floating rate of income. The Fund may also invest in other floating rate debt instruments and investments that are the economic equivalent of floating rate debt instruments. The Fund’s investments may include, but are not limited to, any combination of the following: (i) senior secured floating rate loans or debt; (ii) second lien or

other subordinated or unsecured floating rate loans or debt; and (iii) fixed-rate loans or debt with respect to which the Fund has entered into derivative instruments to effectively convert the fixed-rate interest payments into floating rate interest payments. The Fund may also purchase and sell, without limitation, participations or assignments in senior floating rate loans or second lien floating rate loans.

For purposes of the Fund’s investments, the term debt instruments includes convertible or preferred securities.

The Fund may invest in investments of any credit quality without limitation, including investments rated below investment grade. The Fund anticipates that, under current market conditions, a substantial portion of its portfolio will consist of leveraged loans rated below investment grade and similar investments. These investments are expected to exhibit credit risks similar to high yield securities, which are commonly referred to as “junk bonds.”

The Fund may invest up to 20% of its assets in fixed-rate loans and fixed income securities with respect to which the Fund has not entered into derivative instruments to effectively convert the fixed-rate interest payments into floating-rate interest payments. Such fixed-rate loans and fixed income securities include, but are not limited to, senior loans, second lien loans, corporate bonds, preferred securities, convertible securities, mezzanine investments, collateralized loan obligations, structured products and U.S. government debt securities.

The Fund’s investments in any floating rate and fixed income instruments may be of any duration or maturity. The Fund may invest in loans or debt of foreign issuers, including issuers located in emerging markets, without limitation. The Fund may also invest up to 15% of its net assets in illiquid investments.

The Fund may also invest in companies whose financial condition is uncertain, where the borrower has defaulted in the payment of interest or principal or in the performance of its covenants or agreements, or that may be involved in bankruptcy proceedings, reorganizations or financial restructurings.

The Fund may invest up to 10% of its assets in common stocks or other equity securities. In addition, the Fund may acquire and hold such securities (or rights to acquire such securities) in unit offerings with fixed income securities, in connection with an amendment, waiver, conversion or exchange of fixed income securities, in connection with the bankruptcy

or workout of a distressed fixed income security, or upon the exercise of a right or warrant obtained on account of a fixed income security.

The Fund may buy or sell options or futures on a security or an index of securities, buy or sell options on futures or enter into credit default swaps and interest rate or foreign currency transactions, including swaps and forward contracts (collectively, commonly known as derivatives). The Fund may use derivatives for hedging purposes, but is not required to, as well as to increase the total return on its portfolio investments.

Risk [Heading]

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Summary of Principal Risks

Risk Narrative [Text Block]

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As with any investment, you could lose all or part of your investment in the Fund, and the Fund’s performance could trail that of other investments. The Fund is subject to certain risks, including the principal risks noted below, any of which may adversely affect the Fund’s net asset value per share (“NAV”), trading price, yield, total return and ability to meet its investment objectives. Unlike many exchange-traded funds (“ETFs”), the Fund is not an index-based ETF.

Corporate Loans Risk - Commercial banks and other financial institutions or institutional investors make corporate loans to companies that need capital to grow or restructure. Borrowers generally pay interest on corporate loans at rates that change in response to changes in market interest rates such as the London Interbank Offered Rate (“LIBOR”) or the prime rates of U.S. banks. As a result, the value of corporate loan investments is generally less exposed to the adverse effects of shifts in market interest rates than investments that pay a fixed rate of interest. The market for corporate loans may be subject to irregular trading activity and wide bid/ask spreads. In addition, transactions in corporate loans may settle on a delayed basis. As a result, the proceeds from the sale of corporate loans may not be readily available to make additional investments or to meet the Fund’s redemption obligations. To the extent the extended settlement process gives rise to short-term liquidity needs, the Fund may hold additional cash, sell investments or temporarily borrow from banks and other lenders. The corporate loans in which the Fund invests are usually rated below investment grade.

Senior Loans Risk. There is less readily available, reliable information about most senior loans than is the case for many other types of securities.

An economic downturn generally leads to a higher non‑payment rate, and a senior loan may lose

significant value before a default occurs. Moreover, any specific collateral used to secure a senior loan may decline in value or become illiquid, which would adversely affect the senior loan’s value.

No active trading market may exist for certain senior loans, which may impair the ability of the Fund to realize full value in the event of the need to sell a senior loan and which may make it difficult to value senior loans.

Although senior loans in which the Fund will invest generally will be secured by specific collateral, there can be no assurance that liquidation of such collateral would satisfy the borrower’s obligation in the event of non‑payment of scheduled interest or principal or that such collateral could be readily liquidated. To the extent that a senior loan is collateralized by stock in the borrower or its subsidiaries, such stock may lose all of its value in the event of the bankruptcy of the borrower. Uncollateralized senior loans involve a greater risk of loss. The senior loans in which the Fund invests are usually rated below investment grade. Senior loans made in connection with highly leveraged transactions are subject to greater risks than other senior loans. For example, the risks of default or bankruptcy of the borrower or the risks that other creditors of the borrower may seek to nullify or subordinate the Fund’s claims on any collateral securing the loan are greater in highly leveraged transactions.

Second Lien Loans Risk. Second lien loans generally are subject to similar risks as those associated with investments in senior loans. Because second lien loans are subordinated or unsecured and thus lower in priority of payment to senior loans, they are subject to the additional risk that the cash flow of the borrower and property securing the loan or debt, if any, may be insufficient to meet scheduled payments after giving effect to the senior secured obligations of the borrower.

High Yield Securities Risk. Securities that are rated below investment-grade (commonly referred to as “junk bonds,” which may include those bonds rated below “BBB‑” by S&P Global Ratings (“S&P”) and Fitch Ratings (“Fitch”), or “Baa3” by Moody’s Investors Service, Inc. (“Moody’s”)), or are unrated, may be deemed speculative, may involve greater levels of risk than higher-rated securities of similar maturity and may be more likely to default.

Floating Rate Securities Risk. Securities with floating or variable interest rates can be less sensitive to interest rate changes than securities with fixed

interest rates, but may decline in value if their coupon rates do not reset as high, or as quickly, as comparable market interest rates, and generally carry lower yields than fixed securities of the same maturity. Although floating rate securities are less sensitive to interest rate risk than fixed-rate securities, they are subject to credit risk and default risk, which could impair their value.

Credit Risk. Debt issuers and other counterparties may be unable or unwilling to make timely interest and/or principal payments when due or otherwise honor their obligations. Changes in an issuer’s credit rating or the market’s perception of an issuer’s creditworthiness may also adversely affect the value of the Fund’s investment in that issuer. The degree of credit risk depends on an issuer’s or counterparty’s financial condition and on the terms of an obligation.

Income Risk. Income risk is the risk that the Fund’s yield will vary as short-term securities in its portfolio mature and the proceeds are reinvested in securities with different interest rates.

Interest Rate Risk. During periods of very low or negative interest rates, the Fund may be unable to maintain positive returns or pay dividends to Fund shareholders. Very low or negative interest rates may magnify interest rate risk. Changing interest rates, including rates that fall below zero, may have unpredictable effects on markets, result in heightened market volatility and detract from the Fund’s performance to the extent the Fund is exposed to such interest rates. Additionally, under certain market conditions in which interest rates are low and the market prices for portfolio securities have increased, the Fund may have a very low, or even negative yield. A low or negative yield would cause the Fund to lose money in certain conditions and over certain time periods. An increase in interest rates may cause the value of securities held by the Fund to decline, will generally lead to heightened volatility in the fixed-income markets and may adversely affect the liquidity of certain fixed-income investments, including those held by the Fund. The historically low interest rate environment heightens the risks associated with rising interest rates.

Call Risk. During periods of falling interest rates, an issuer of a callable bond held by the Fund may “call” or repay the security before its stated maturity, and the Fund may have to reinvest the proceeds in securities with lower yields, which would result in a decline in the Fund’s income, or in securities with greater risks or with other less favorable features.

Extension Risk. During periods of rising interest rates, certain debt obligations may be paid off substantially more slowly than originally anticipated and the value of those securities may fall sharply, resulting in a decline in the Fund’s income and potentially in the value of the Fund’s investments.

Prepayment Risk. When interest rates fall, certain obligations will be paid off by the obligor more quickly than originally anticipated, and the Fund may have to invest the proceeds in securities with lower yields.

Asset Class Risk. Securities and other assets in the Fund’s portfolio may underperform in comparison to the general financial markets, a particular financial market or other asset classes.

Assets Under Management (AUM) Risk. From time to time, an Authorized Participant (as defined in the Creations and Redemptions section of this prospectus (the “Prospectus”) a third-party investor, the Fund’s adviser or an affiliate of the Fund’s adviser, or a fund may invest in the Fund and hold its investment for a specific period of time in order to facilitate commencement of the Fund’s operations or to allow the Fund to achieve size or scale. There can be no assurance that any such entity would not redeem its investment or that the size of the Fund would be maintained at such levels, which could negatively impact the Fund.

Authorized Participant Concentration Risk. Only an Authorized Participant (as defined in the Creations and Redemptions section of this Prospectus) may engage in creation or redemption transactions directly with the Fund, and none of those Authorized Participants is obligated to engage in creation and/or redemption transactions. The Fund has a limited number of institutions that may act as Authorized Participants on an agency basis (i.e., on behalf of other market participants). To the extent that Authorized Participants exit the business or are unable to proceed with creation or redemption orders with respect to the Fund and no other Authorized Participant is able to step forward to create or redeem, Fund shares may be more likely to trade at a premium or discount to NAV and possibly face trading halts or delisting.

Collateralized Debt Obligations Risk - In addition to the typical risks associated with fixed-income securities and asset-backed securities, collateralized debt obligations (“CDOs”) carry additional risks including, but not limited to: (i) the possibility that distributions from collateral securities will not be

adequate to make interest or other payments; (ii) the risk that the collateral may default or decline in value or be downgraded, if rated by a nationally recognized statistical rating organization; (iii) the Fund may invest in tranches of CDOs that are subordinate to other tranches; (iv) the structure and complexity of the transaction and the legal documents could lead to disputes among investors regarding the characterization of proceeds; (v) the investment return achieved by the Fund could be significantly different than those predicted by financial models; (vi) the lack of a readily available secondary market for CDOs; (vii) the risk of forced “fire sale” liquidation due to technical defaults such as coverage test failures; and (viii) the CDO’s manager may perform poorly.

Concentration Risk. The Fund may be susceptible to an increased risk of loss, including losses due to adverse events that affect the Fund’s investments more than the market as a whole, to the extent that the Fund’s investments are concentrated in the securities and/or other assets of a particular issuer or issuers, country, group of countries, region, market, industry, group of industries, sector, market segment or asset class.

Convertible Securities Risk. The market price of a convertible security generally tends to behave like that of a regular debt security; that is, if market interest rates rise, the value of a convertible security usually falls. In addition, convertible securities are subject to the risk that the issuer will not be able to pay interest, principal or dividends when due, and their market value may change based on changes in the issuer’s credit rating or the market’s perception of the issuer’s creditworthiness. Because a convertible security derives a portion of its value from the common stock into which it may be converted, a convertible security is also subject to the same types of market and issuer risks that apply to the underlying common stock, including the potential for increased volatility in the price of the convertible security.

Cybersecurity Risk. Failures or breaches of the electronic systems of the Fund, the Fund’s adviser, distributor, and other service providers (including the benchmark provider), market makers, Authorized Participants or the issuers of securities in which the Fund invests have the ability to cause disruptions, negatively impact the Fund’s business operations and/or potentially result in financial losses to the Fund and its shareholders. While the Fund has established business continuity plans and risk management systems seeking to address system breaches or failures, there are inherent limitations in such plans

and systems. Furthermore, the Fund cannot control the cybersecurity plans and systems of the Fund’s service providers, market makers, Authorized Participants or issuers of securities in which the Fund invests.

Distressed Securities Risk. Distressed securities are speculative and involve substantial risks in addition to the risks of investing in junk bonds. The Fund will generally not receive interest payments on the distressed securities and may incur costs to protect its investment. In addition, distressed securities involve the substantial risk that principal will not be repaid. These securities may present a substantial risk of default or may be in default at the time of investment. The Fund may incur additional expenses to the extent it is required to seek recovery upon a default in the payment of principal of or interest on its portfolio holdings. In any reorganization or liquidation proceeding relating to a portfolio holding, the Fund may lose its entire investment or may be required to accept cash or securities with a value less than its original investment. Distressed securities and any securities received in an exchange for such securities may be subject to restrictions on resale.

Dividend Risk. Because certain of the corporate loans held by the Fund will have floating or variable interest rates, the amounts of the Fund’s monthly distributions to its stockholders are expected to vary with fluctuations in market interest rates. Generally, when market interest rates fall, the amount of the distributions to stockholders will likewise decrease.

Equity Securities Risk. Stock markets are volatile. The price of equity securities fluctuates based on changes in a company’s financial condition and overall market and economic conditions.

Event Risk. Event risk is the risk that corporate issuers may undergo restructurings, such as mergers, leveraged buyouts, takeovers, or similar events financed by increased debt. As a result of the added debt, the credit quality and market value of a company’s bonds and/or other debt securities may decline significantly.

Forward Foreign Currency Exchange Contracts. Forward foreign currency exchange transactions are over‑the‑counter (“OTC”) contracts to purchase or sell a specified amount of a specified currency or multinational currency unit at a price and future date set at the time of the contract. Forward foreign currency exchange contracts do not eliminate fluctuations in the value of non‑U.S. securities but rather allow the Fund to establish a fixed rate of

exchange for a future point in time. This strategy can have the effect of reducing returns and minimizing opportunities for gain.

Futures Contract Risk. Futures are standardized, exchange-traded contracts that obligate a purchaser to take delivery, and a seller to make delivery, of a specific amount of an asset at a specified future date at a specified price. Unlike equities, which typically entitle the holder to a continuing ownership stake in a corporation, futures contracts normally specify a certain date for settlement in cash based on the level of the reference rate. The primary risks associated with the use of futures contracts, or swaps or other derivatives referencing futures contracts, are: (i) the imperfect correlation between the change in market value of the instruments or swaps or other derivatives referencing futures contracts held by the Fund and the price of the futures contract; (ii) possible lack of a liquid secondary market for a futures contract and the resulting inability to close a futures contract when desired; (iii) losses caused by unanticipated market movements, which are potentially unlimited; (iv) BFA’s inability to predict correctly the direction of prices and other economic factors; and (v) the possibility that the counterparty will default in the performance of its obligations.

Illiquid Investments Risk. The Fund may not acquire any illiquid investment if, immediately after the acquisition, the Fund would have invested more than 15% of its net assets in illiquid investments. An illiquid investment is any investment that the Fund reasonably expects cannot be sold or disposed of in current market conditions in seven calendar days or less without significantly changing the market value of the investment. To the extent the Fund holds illiquid investments, the illiquid investments may reduce the returns of the Fund because the Fund may be unable to transact at advantageous times or prices. In addition, if the Fund is limited in its ability to sell illiquid investments during periods when shareholders are redeeming their shares, the Fund will need to sell liquid securities to meet redemption requests and illiquid securities will become a larger portion of the Fund’s holdings. During periods of market volatility, liquidity in the market for the Fund’s shares may be impacted by the liquidity in the market for the underlying securities or instruments held by the Fund, which could lead to the Fund’s shares trading at a premium or discount to the Fund’s NAV.

Infectious Illness Risk. A widespread outbreak of an infectious illness, such as the COVID-19 pandemic, may result in travel restrictions, disruption of healthcare services, prolonged quarantines,

cancellations, supply chain disruptions, business closures, lower consumer demand, layoffs, ratings downgrades, defaults and other significant economic, social and political impacts. Markets may experience temporary closures, extreme volatility, severe losses, reduced liquidity and increased trading costs. Such events may adversely affect the Fund and its investments and may impact the Fund’s ability to purchase or sell securities or cause elevated tracking error and increased premiums or discounts to the Fund’s NAV. Despite the development of vaccines, the duration of the COVID-19 pandemic and its effects cannot be predicted with certainty.

Issuer Risk. The performance of the Fund depends on the performance of individual securities to which the Fund has exposure. The Fund may be adversely affected if an issuer of underlying securities held by the Fund is unable or unwilling to repay principal or interest when due. Changes in the financial condition or credit rating of an issuer of those securities may cause the value of the securities to decline.

Large Shareholder and Large-Scale Redemption Risk. Certain shareholders, including an Authorized Participant, a third-party investor, the Fund’s adviser or an affiliate of the Fund’s adviser, a market maker, or another entity, may from time to time own or manage a substantial amount of Fund shares, or may invest in the Fund and hold its investment for a limited period of time. There can be no assurance that any large shareholder or large group of shareholders would not redeem their investment. Redemptions of a large number of Fund shares could require the Fund to dispose of assets to meet the redemption requests, which can accelerate the realization of taxable income and/or capital gains and cause the Fund to make taxable distributions to its shareholders earlier than the Fund otherwise would have. In addition, under certain circumstances, non‑redeeming shareholders may be treated as receiving a disproportionately large taxable distribution during or with respect to such year. In some circumstances, the Fund may hold a relatively large proportion of its assets in cash in anticipation of large redemptions, diluting its investment returns. These large redemptions may also force the Fund to sell portfolio securities when it might not otherwise do so, which may negatively impact the Fund’s NAV, increase the Fund’s brokerage costs and/or have a material effect on the market price of the Shares.

Leverage Risk. Some transactions may give rise to a form of economic leverage. These transactions may include, among others, derivatives, and may expose

the Fund to greater risk and increase its costs. The use of leverage may cause the Fund to liquidate portfolio positions when it may not be advantageous to do so to satisfy its obligations or to meet the applicable requirements of the Investment Company Act and the rules thereunder. Increases and decreases in the value of the Fund’s portfolio will be magnified when the Fund uses leverage.

Libor Risk. The Fund may be exposed to financial instruments that are tied to LIBOR to determine payment obligations, financing terms, hedging strategies or investment value. As part of the phase-out of the use of LIBOR, the rate’s administrator, ICE Benchmark Administration Limited (“IBA”), discontinued two USD LIBOR settings immediately after publication on December 31, 2021. The United Kingdom’s Financial Conduct Authority (“FCA”), which regulates LIBOR, and IBA previously announced that a majority of USD LIBOR settings will no longer be published after June 30, 2023. Various financial industry groups continue planning for the transition away from LIBOR, but there are challenges to converting certain securities and transactions to a new reference rate. Neither the effect of the LIBOR transition process nor its ultimate success can yet be known. The transition process might lead to increased volatility and illiquidity in markets for, and reduce the effectiveness of new hedges placed against, instruments whose terms currently include LIBOR. There may be significant uncertainty regarding the effectiveness of any alternative methodologies to replicate LIBOR. All of the aforementioned may adversely affect the Fund’s performance or NAV.

Management Risk. The Fund is subject to management risk, which is the risk that the investment process, techniques and risk analyses applied by BFA will not produce the desired results, and that securities selected by BFA may underperform the market or any relevant benchmark. In addition, legislative, regulatory, or tax developments may affect the investment techniques available to BFA in connection with managing the Fund and may also adversely affect the ability of the Fund to achieve its investment objectives.

Market Risk. The Fund could lose money over short periods due to short-term market movements and over longer periods during more prolonged market downturns. Local, regional or global events such as war, acts of terrorism, the spread of infectious illness or other public health issues, recessions, or other events could have a significant impact on the Fund and its investments and could result in increased premiums or discounts to the Fund’s NAV.

Market Trading Risk. The Fund faces numerous market trading risks, including the potential lack of an active market for Fund shares, losses from trading in secondary markets, periods of high volatility and disruptions in the creation/redemption process. Unlike some ETFs that track specific indexes, the Fund does not seek to replicate the performance of a specified index. Index-based ETFs have generally traded at prices that closely correspond to NAV per share. Given the high level of transparency of the Fund’s holdings, BFA believes that the trading experience of the Fund should be similar to that of index-based ETFs. However, ETFs that do not seek to replicate the performance of a specified index have a limited trading history and, therefore, there can be no assurance as to whether, and/or the extent to which, the Fund’s shares will trade at premiums or discounts to NAV. ANY OF THESE FACTORS, AMONG OTHERS, MAY LEAD TO THE FUND’S SHARES TRADING AT A PREMIUM OR DISCOUNT TO NAV.

Mezzanine Securities Risk. Mezzanine securities carry the risk that the issuer will not be able to meet its obligations and that the equity securities purchased with the mezzanine investments may lose value.

Operational Risk. The Fund is exposed to operational risks arising from a number of factors, including, but not limited to, human error, processing and communication errors, errors of the Fund’s service providers, counterparties or other third parties, failed or inadequate processes and technology or systems failures. The Fund and BFA seek to reduce these operational risks through controls and procedures. However, these measures do not address every possible risk and may be inadequate to address significant operational risks.

Options. An option is an agreement that, for a premium payment or fee, gives the option holder (the purchaser) the right but not the obligation to buy (a “call option”) or sell (a “put option”) the underlying asset (or settle for cash in an amount based on an underlying asset, rate, or index) at a specified price (the “exercise price”) during a period of time or on a specified date. Investments in options are considered speculative. When the Fund purchases an option, it may lose the total premium paid for it if the price of the underlying security or other assets decreased, remained the same or failed to increase to a level at or beyond the exercise price (in the case of a call option) or increased, remained the same or failed to decrease to a level at or below the exercise price (in the case of a put option). If a put or call option purchased by the Fund were permitted to expire without being sold or exercised, its premium would

represent a loss to the Fund. To the extent that the Fund writes or sells an option, if the decline or increase in the underlying asset is significantly below or above the exercise price of the written option, the Fund could experience a substantial loss.

Non‑U.S. Issuers Risk. Securities issued by non‑U.S. issuers carry different risks from securities issued by U.S. issuers. These risks include differences in accounting, auditing and financial reporting standards, the possibility of expropriation or confiscatory taxation, adverse changes in investment or exchange control regulations, political instability, regulatory and economic differences, and potential restrictions on the flow of international capital.

Preferred Securities Risk. Preferred securities may pay fixed or adjustable rates of return. Preferred securities are subject to issuer-specific and market risks applicable generally to equity securities. In addition, a company’s preferred securities generally pay dividends only after the company makes required payments to holders of its bonds and other debt. For this reason, the value of preferred securities will usually react more strongly than bonds and other debt to actual or perceived changes in the company’s financial condition or prospects. Preferred securities of smaller companies may be more vulnerable to adverse developments than preferred securities of larger companies.

Risk of Investing in Emerging Markets. Investments in emerging market issuers may be subject to a greater risk of loss than investments in issuers located or operating in more developed markets. Emerging markets may be more likely to experience inflation, political turmoil and rapid changes in economic conditions than more developed markets. Companies in many emerging markets are not subject to the same degree of regulatory requirements, accounting standards or auditor oversight as companies in more developed countries, and as a result, information about the securities in which the Fund invests may be less reliable or complete. Emerging markets often have less reliable securities valuations and greater risk associated with custody of securities than developed markets. There may be significant obstacles to obtaining information necessary for investigations into or litigation against companies and shareholders may have limited legal remedies. The Fund is not actively managed and does not select investments based on investor protection considerations.

Risk of Investing in the U.S. Certain changes in the U.S. economy, such as when the U.S. economy

weakens or when its financial markets decline, may have an adverse effect on the securities to which the Fund has exposure.

Risk of Swap Agreements. A swap is a two‑party contract that generally obligates each counterparty to exchange periodic payments based on a pre‑determined underlying investment or notional amount and to exchange collateral to secure the obligations of each counterparty. Swaps may be leveraged and are subject to counterparty risk, credit risk and pricing risk. Swaps may be subject to illiquidity risk, and it may not be possible for the Fund to liquidate a swap position at an advantageous time or price, which may result in significant losses. Certain standardized interest rate and credit default swaps are required to be traded on an exchange or trading platform and centrally cleared. Most other swaps are entered into a negotiated, bi‑lateral basis and traded in the over‑the counter market. Swaps are subject to bi‑lateral variation margin. Initial margin requirements are in the process of being phased in, and the Fund may be subject to such requirements as early as September 2022. These requirements may raise the costs for the Fund’s investment in swaps.

Small Fund Risk. When the Fund’s size is small, the Fund may experience low trading volume and wide bid/ask spreads. In addition, the Fund may face the risk of being delisted if the Fund does not meet certain conditions of the listing exchange. Any resulting liquidation of the Fund could cause the Fund to incur elevated transaction costs for the Fund and negative tax consequences for its shareholders.

Structured Products Risk. Holders of structured products bear risks of the underlying investments, index or reference obligation and are subject to counterparty risk. The Fund may have the right to receive payments only from the structured product, and generally does not have direct rights against the issuer or the entity that sold the assets to be securitized. Certain structured products may be thinly traded or have a limited trading market. In addition to the general risks associated with debt securities discussed herein, structured products carry additional risks, including, but not limited to: the possibility that distributions from collateral securities will not be adequate to make interest or other payments; the quality of the collateral may decline in value or default; and the possibility that the structured products are subordinate to other classes. Structured notes are based upon the movement of one or more factors, including currency exchange rates, interest rates, reference bonds and stock indices, and

changes in interest rates and impact of these factors may cause significant price fluctuations. Additionally, changes in the reference instrument or security may cause the interest rate on the structured note to be reduced to zero.

U.S. Government Issuer Risk. Treasury obligations may differ in their interest rates, maturities, times of issuance and other characteristics. Obligations of U.S. Government agencies and authorities are supported by varying degrees of credit but generally are not backed by the full faith and credit of the U.S. Government. No assurance can be given that the U.S. Government will provide financial support to its agencies and authorities if it is not obligated by law to do so.

Valuation Risk. The price the Fund could receive upon the sale of a security or other asset may differ from the Fund’s valuation of the security or other asset, particularly for securities or other assets that trade in low volume or volatile markets or that are valued using a fair value methodology as a result of trade suspensions or for other reasons. Because non-U.S. exchanges may be open on days when the Fund does not price its shares, the value of the securities or other assets in the Fund’s portfolio may change on days or during time periods when shareholders will not be able to purchase or sell the Fund’s shares.

Authorized Participants who purchase or redeem Fund shares on days when the Fund is holding fair-valued securities may receive fewer or more shares, or lower or higher redemption proceeds, than they would have received had the Fund not fairvalued securities or used a different valuation methodology. The Fund’s ability to value investments may be impacted by technological issues or errors by pricing services or other third-party service providers.

Risk Lose Money [Text]

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As with any investment, you could lose all or part of your investment in the Fund, and the Fund’s performance could trail that of other investments.

Bar Chart and Performance Table [Heading]

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Performance Information

Performance Narrative [Text Block]

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Because the Fund has not commenced operations as of the date of this Prospectus, it does not have performance information an investor would find useful in evaluating the risks of investing in the Fund. The Fund’s benchmark is Morningstar LSTA Leverage Loan Index.

Performance One Year or Less [Text]

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BlackRock Floating Rate Loan ETF | BlackRock Floating Rate Loan ETF

Risk/Return:

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Management Fees

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0.60%

^[1],[2]

Distribution and Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

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none

Total Annual Fund Operating Expenses

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0.60%

Fee Waiver

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(0.05%)

^[1],[2]

Total Annual Fund Operating Expenses After Fee Waiver

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0.55%

^[1],[2]

1 Year

rr_ExpenseExampleYear01

$ 53

3 Years

rr_ExpenseExampleYear03

$ 176

[1]	As described in the “Management” section of the Fund’s prospectus beginning on page 16, BFA has contractually agreed to waive 0.05% of its management fee through June 30, 2026. The agreement may be terminated upon 90 days’ notice by a majority of the non‑interested trustees of the Trust or by a vote of a majority of the outstanding voting securities of the Fund.
[2]	As described in the “Management” section of the Fund’s prospectus beginning on page 16, BFA has contractually agreed to waive its management fees by the amount of investment advisory fees the Fund pays to BFA indirectly through its investment in money market funds managed by BFA or its affiliates, through June 30, 2024.