They'll require all publishers of upcoming PlayStation, Xbox and Switch games to reveal the chances of earning rare items. Some publishers do so already, and several others have agreed to make the disclosures in their forthcoming titles. Those who have signed up include Activision Blizzard, Bandai Namco, Bethesda, Bungie, EA, Take-Two Interactive, Ubisoft, Wizards of the Coast and Warner Bros.
The initiative doesn't extend to other platforms, with PC being the major omission. Still, you can probably expect some publishers to disclose loot box odds there too.
Gaming industry group the Entertainment Software Association (which runs E3) announced the measure Wednesday at a Federal Trade Commission workshop on loot box consumer protection issues. The timeline of rolling out the disclosures is in flux, but Sony, Nintendo and Microsoft are hoping to have them in place by next year.
"I am encouraged that the video game industry has taken this important step forward to improve loot box transparency," Senator Maggie Hassan, who has raised concerns about loot boxes with the FTC and the Entertainment Software Rating Board, told Engadget in a statement. "I'll keep working to ensure that children are protected from the predatory and addictive effects of loot boxes in video games."
Update 8/7/2019 5:15 PM ET: Added Senator Hassan's remarks.