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Add an indicator for watched videos on YouTube. Use GM menus to display history statistics, backup history, and restore/merge history.
< Mark Watched YouTube Videos 피드백
I did notice an error on the calculation. I've corrected it on the script update, hopefully.
The update also added time span of the watch history in the statistics, as well as changed the maximum age of watched video in history from 5 years to 10 years (any entry older than maximum, will be removed).
Great script.
Minor problem: Seems like something in the statistics isn't quite working as intended. My average videos viewed per year is only about 6x the per year, instead of 12x.