Sign in to YouTube Studio
Go to your channel
Click your profile icon (top right)
Select YouTube Studio
In the left menu, click Analytics
Click Subscribers
Review the subscriber list and subscriber metrics shown on the page
To see subscriber activity, use the filters and tabs within Analytics (if available)
To view who subscribed (if available), go to YouTube Studio
In the left menu, click Community
Look for a Subscribers or Subscriber notifications section (availability can vary by account)
Use the search/filter options in that section (if shown)