Log on to real estate sites like Zillow or Redfin, and you’ll discover the era of one-click homebuying has arrived. You can search real estate listings, determine property values, and even buy or sell homes directly on the platforms. Now even the task of securing a mortgage, which used to take weeks of paperwork and phone calls, can be completed on the site just as easily as scrolling through a property’s photo gallery.

But experts warn this apparent efficiency is masking a system designed to steer homebuyers to the platforms’ own mortgage lenders, squeezing out competition and discouraging buyers from finding cheaper options. It’s part of massive consolidation and restructuring efforts by Zillow and Redfin’s corporate owners to corner the trillion-dollar mortgage market, which is already driving up housing costs and could heighten the risk of a financial crisis.

Regulators have even accused Zillow and Redfin’s parent companies of illegally rewarding real estate agents for directing buyers to their in-house mortgage lenders — something that the top consumer financial watchdog under President Joe Biden called a “kickback scheme.”