IEX Group, the equity and options exchange operator, has grown market share in equities by more than 60% since July last year and is the fastest growing exchange, according to Bloomberg Intelligence.

Matt Weinberg, co-head of equities at IEX, told Markets Media that the firm is gaining share in both displayed and dark markets. Market share in equities grew from 2.75% in July 2025 to over 5% in the last half of October 2026, according to Weinberg. He added: “This is unique because IEX is the only venue where we are about 50-50 dark vs displayed.”

IEX is the fastest-growing exchange and now the fourth largest by volume behind Nasdaq, NYSE Arca and NYSE, according to Bloomberg’s Market Structure Weekly report on 19 October 2026.

Bloomberg said the recent launch of the Texas Stock Exchange (TXSE) and 24X brings the number of U.S. equity exchanges to 18.

Displayed share 

Weinberg said IEX’s displayed share is up fivefold since June 2024. He claimed this is due to IEX delivering better performance for investors with its D-Limit order.

IEX introduced its Discretionary Limit, or D-Limit, order type in 2020. D-Limit protects liquidity providers from potential adverse selection resulting from latency arbitrage trading strategies and was launched to encourage members to submit more displayed limit orders to the exchange. D-Limit uses the power of the IEX Signal to move an order out of the way if the price is about to become imminently stale, i.e. the order avoids being “run over” when the price is unstable.

IEX’s Signal, or crumbling quote indicator (CQI), is a machine learning-based mathematical formula,  The Signal predicts which way the market will move in order to protect customers from trading at a price that will imminently become stale.

Sam Stevens, head of analytics at IEX, told Markets Media that there has been a “marked pickup” in the use of D-Limit in the last couple of years. He said: “Liquidity begets liquidity and that has encouraged more adoption across a broader group of participants, creating a virtuous cycle.”

Stevens added that nearly three quarters, 72%, of D-Limit volume gets true spread capture, i.e. trades at the National Best Bid and Offer for which there is no change to the NBBO in the two milliseconds following a trade. In constrast, at other maker-taker venues this is less than 30%.

In addition, Stevens said IEX has the largest quote size in many S&P 500 names such as F (Ford), AAL, and NFLX, which is even larger than the primary listing venue and argued this is a testament to the protection that D-Limit offers.

“An institutional broker using D-Limit to bid at 10 can get filled at a better price,” said Stevens. “Price improvement averages more than 0.5 cents per share per share across all institutional D-Limit volume, with 23% of this volume receiving on average 2.5 cents per share, which is really material.”

In addition, Weinberg claimed that  the new version of the CQI Signal that came out at the end of August this year has contributed to an improvement performance.

“If a broker is getting half a penny of price improvement on the child slice of a displayed order, you can imagine the benefit to the performance of the parent order,” added Weinberg. “This unique D-Limit functionality has driven our displayed growth.”

In algorithmic trading, a large parent order is split into numerous small child orders in order to minimise market impact and improve execution quality.

Dark performance

Weinberg said IEX also continues to iterate on its dark performance and has launched an Ultra-Passive Signal, an optional signal for IEX’s flagship non-displayed D-Peg order.

Stevens explained there is an explicit trade-off that investors make between the expected fill rate of an order and the quality of the fills. There are certain situations when investors want to be more passive and place a very high value on quality, and the Ultra-Passive Signal was designed for this situation.

“The feedback from clients is that the Ultra-Passive Signal is delivering materially better performance, which is part of the reason why we are now the largest notional midpoint venue for single stocks across alternative trading systems [ATSs] or exchanges,” added Weinberg.

Across the equities industry, there is increasing focus on trading around the close. Weinberg claimed that due to IEX’s unique structure of being 50-50 in displayed and dark, the firm can ramp into the close materially more than any other non-primary venue. He added: “Our highest market share minute of the day is 3:58.”

IEX will  continue to make additional improvements that it believes deliver better performance, both in displayed and dark trading.

“Being the biggest notional midpoint venue for single stocks allows investors to source clean liquidity and minimize their impact,” Weinberg added.