YouTube will now show ads at the end of all monetizing videos over 10 minutes long by default, but can be turned off by creators.
Post-roll ads are between 12 seconds and three minutes long. Showing at the end of the video, they will likely not affect most viewing experiences, except perhaps playlists.
Earlier this year, YouTube lowered the threshold for mid-rolls from 10 minutes to 8. Now pre-roll, mid-roll and post-roll ads are all turned on by default.
Those eligible for monetization can choose between any combination of pre-roll, mid-roll and post-roll ads for videos over 10 minutes long. Post-roll ads can be turned off during upload or on existing videos within the monetization tab. Here creators can also turn off pre-roll and mid-roll ads by default.