The government says about 9.2 million people signed up for coverage this year through HealthCare.gov, the health insurance website serving most states.
The preliminary numbers out Friday don't include figures from 11 states that run their own health insurance markets, so the final national number will be higher.
Nonetheless, the report shows slippage from last year, when about 500,000 more customers enrolled in the states served by HealthCare.gov.
The insurance markets created by former President Barack Obama's law provide subsidized coverage for people who don't have access to health care through their jobs.
This year's report is being closely followed, with President Donald Trump vowing to repeal and replace the Obama-era law.
Premiums were up, choice of insurers went down, and the Trump administration pulled ads aimed at the uninsured.