99designs’ private contests require you to agree to an NDA. This is a legal agreement between a customer who’s holding a private contest, and the designers who want to see the details of that contest.
When you agree to the NDA, you’re agreeing not to disclose the details of the contest to anyone else.
You may also be agreeing to other terms, since 99designs customers can upload their own NDAs to cover private contests. So it’s important to read and understand the NDA fully before you agree to it. Most commonly, customers use this standard NDA template to protect their 99designs contests.