YouTube announced that it is introducing a major change to how it publicly shows the subscriber count on channels.
Starting August 2019, YouTube will start showing the abbreviated subscriber number across all desktop and mobile apps for channels with more than 1,000 subscribers. Those with fewer subscribers will be shown non-abbreviated count; for instance, the abbreviated count will be shown as 133k and in some places, it will display the full count, e.g., 133,017.
Third-parties using YouTube API services will also access the same public-facing counts you see on YouTube. Meanwhile, creators will be able to see the exact number in YouTube Studio.