Paid-for subscriptions would mean fans of YouTube star Zoella could watch her videos without the interruption of ads.
Re/code reports Wojcicki said: "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"
Just like Pandora and Spotify before it, there are just two options left on the table for users: you choose ads, or you choose to pay a fee to remove them. Wojcicki declined to offer details on when it might open up subscriptions, but did say she is "optimistic about seeing it soon."
The likely consequence of building in an ad-free subscription service is a higher ad load on the free service. In other words, just enough extra intrusive ads to tempt you into paying to remove them.
YouTube does already offer a paid-for subscription service, but it's not ad free. Last year YouTube let individual content creators sell subscriptions on to users at fees starting from $0.99 per month, for access to content like full episodes of Sesame Street or classic UFC fights.
Wojcicki also used her appearance at the conference to reveal that half of all YouTube views now come from mobile devices and that watch time is growing at a rate of 50% year on year.
Google has always been cagey about revealing how much of an impact YouTube has on its financials, and does not split out income from the video service in its quarterly results. Research firm eMarketer has estimated YouTube generated $5.6 billion in gross ad revenue last year - which would equal 9.7% of the $57.86 billion in revenue the company reported for the fiscal year 2013.