Whether you’re looking to sell or buy a home, you will no doubt encounter the multiple listing service, or MLS. The site and service are, in many ways, the very lifeblood of the real estate business.

Compass will share select off-MLS listings with Redfin under a new three-year agreement that could alter how some properties are marketed.

MLS executives warn a national MLS faces data, governance and antitrust hurdles, while a federation model could expand access.