It's hard to see the value in post-roll, but YouTube is hoping that some advertisers will find the format useful after its decision to insert ads at the end of some of its clips.

The post-roll ads will play automatically at the end of a video, marking a departure from the previous practice of playing ads only when a user clicked on an overlay ad in the middle of the video.

The ads will play on about 4 percent of all YouTube videos.

While post-roll is considered far less intrusive than pre-roll, questions remain about whether it delivers enough value to advertisers.

YouTube has been working feverishly to come up with a workable ad model in the past year. While it remains the dominant video player on the market in terms of audience, the Google-owned company has seen coveted advertisers cast a keener eye toward rival Hulu, which has aggressively been promoting itself as the destination for quality, long-form video on the web.