How much would you pay for ad-free YouTube videos?

Google (GOOGL) acknowledged late Monday that it is considering a subscription service that would allow viewers to skip the ads that run before many YouTube videos.

That move would dramatically change the revenue model for the video colossus. Most of YouTube's services are free, so the site largely relies on advertising to pay the bills.

"YouTube right now is ad-supported, which is great because it has enabled us to scale to a billion users; but there's going to be a point where people don't want to see the ads," YouTube CEO Susan Wojcicki said at a conference sponsored by the website ReCode, which posted about her comments.

She called a subscription arrangement "an interesting model" and added that YouTube is "thinking about how to give users options," according to ReCode.

Rumors about paid YouTube subscriptions have swirled for years. Its competitors include subscription video services like Netflix (NFLX) and Hulu and music subscription services such as Spotify and Pandora (P). (Some of YouTube's most popular content includes music and music videos.)

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Wojcicki didn't mention how much the subscription would cost or when it would become available.

Meanwhile, Google is facing some challenges in its advertising business. Advertisers aren't paying as much as they used to for standard mobile ads, for example.

Most Google services, like Gmail email and Drive cloud storage, are available for free. Users can pay a premium to upgrade.

YouTube does offer a paid subscriptions on a limited scale. It allows content creators to charge for access to videos they post.