Doesn't include game streaming services like GeForce NOW. I.e. the game must be rendered on the device itself.

It doesn't need to run in all browsers - e.g. if it runs in desktop browsers, but not on mobile browsers, this market would still resolve to YES. If it runs in Chrome, but not in Safari, this market would still resolve to YES.

Must be an official version of the game - i.e. not a community-ported client, or anything like that.

It's okay if it's experimental so long as the full game (more or less) has been officially demonstrated or claimed by either company to be working within a web browser. If they've merely announced that it will run in a web browser in the future or that they're working on browser port, then that doesn't count. The game must actually run in a browser before Jan 1st 2027 and be verifiable via actually playing it, or official company statements.