Last month, Microsoft introduced a new Canary channel to the Windows Insider program, alongside Dev, Beta and Release Preview. The Redmond giant first introduced Channels or Rings back in 2014, where there was the Fast Ring (later called Dev Channel) and a Slow Ring (later renamed to Beta Channel). There was a Canary Ring too, but it was not public and only indicated internal testing by the Microsoft Operating Systems Group (OSG). Later on came the Release Preview Ring (Channel) in 2016.
As the Dev Channel was already getting the newest features for Windows 11, many enthusiasts would probably have expected that the new Canary channel to be the testing ground for the future of Windows, perhaps related to early Next Valley (Windows 12) evaluation. However, that wasn't the case, at least not initially, as the Canary and Dev Channel have both been used for assessing features expected to be generally available around the same time frame.
That might change soon, however, as the Canary channel has now received a bump up in its build number. Spotted by Twitter user Xeno, the Canary channel has seemingly gone from Build 253xx to Build 258xx nomenclature. Although this is entirely speculation on our end, perhaps Microsoft might be gearing up to push more newer features out, perhaps those expected with Windows 11 23H2 (Moment 4) and even Windows 12.