The exchange is where the orders are executed, but the exchange doesn't execute the orders. The market makers do that job. Look at the companies listed in the

The exchange is where the orders are executed, but the exchange doesn't execute the orders. The market makers do that job. Look at the companies listed in the disclosures. Citadel appears to have the largest share in all of the examples listed. Their website [1] claims that: > We act as a specialist or market maker in more than 3,000 U.S. listed-options names, representing 99% of traded volume, and rank as a top liquidity provider on the major U.S. options exchanges, executing approximately 39% of all U.S.-listed retail volume, making us the industry’s top wholesale market maker. Citadel is paying Robinhood to put your limit order into their system at the NYSE or NASDAQ or whatever other exchange and then they handle the execution of it. Also, I don't believe that this article is claiming that Citadel et al are the high frequency traders, but that the high frequency traders are connected to their platforms and profiting (in some unspecified manner) from the orders that come in. [1] https://www.citadelsecurities.com/products/equities-and-options/ https://www.citadelsecurities.com/products/equities-and-opti...