YouTube has recently added a new 144p video resolution option for select videos, according to users who noticed the change.
Up until this option was added, YouTube made playback quality from 240p to 4K resolution available. While these higher resolutions offer pristine quality, they do require significant bandwidth and fast internet connections.
We speculate that this new 144P option is a move to address these issues. This new base choice will open up YouTube video viewing in countries and regions where people are limited to basic internet connections.