Microsoft’s How-Old.net tool, which guesses a person’s age and gender based on a photo of their face, became a viral hit despite (or, more likely, because of) its comically spotty accuracy. But before you submit your own photo, check the fine print: Your face could end up in a future Microsoft advertisement, Twitter user @Waldo points out .

The text in question reads:

However, by posting, uploading, inputting, providing, or submitting your Submission, you are granting Microsoft, its affiliated companies, and necessary sublicensees permission to use your Submission in connection with the operation of their Internet businesses (including, without limitation, all Microsoft services), including, without limitation, the license rights to: copy, distribute, transmit, publicly display, publicly perform, reproduce, edit, translate, and reformat your Submission; to publish your name in connection with your Submission; and to sublicense such rights to any supplier of the Website Services.

That fine print, from the Terms of Service for Microsoft’s Azure cloud platform, means that Microsoft can use your photos on its websites and in advertising, and it can give its suppliers the same rights to your image.

How-Old.net was trotted out by Microsoft VP of cloud and enterprise Joseph Sirosh during this week’s Microsoft Build conference. Sirosh said How-Old.net was created as a quick demo playing with Microsoft’s Face Detection API. The tool’s viral success pushed two Microsoft engineers who helped build How-Old.net to use the site as a test case for explaining how easy it is to build sites on the Microsoft Azure cloud platform. (How-Old.net took only a day to build, yet incorporates streaming analytics and real-time business intelligence.)

Of course, building How-Old.net on top of Microsoft Azure means all those photos ingested are subject to the Microsoft Azure Terms of Service, which means Microsoft can use those photos pretty much however it wants. Will Microsoft use all those faces in an ad? Probably not, but it’s a possibility.

Update 5/4/15 8:24 a.m. — A Microsoft spokesperson reached out to Fast Company with additional information:

We wanted to let you know that http://how-old.net does not store or share pictures or personally identifiable information (PII). The Terms of Service are accurate and like those of other companies. Developers get to choose how their apps work. The developers of How-old.net chose not to store or share photos for this app.

[via Brandon Wall]