It depends on the type of project. For design projects, our advice is to always ask for the file in vector format. However, in general it is best to use the dedicated section on the site to communicate with the winner and agree upon the file format you require. This section will be available within the project once the winner has been selected. It is however always advisable, if the project requires the delivery of content, to specify the desired file format in the Contest Brief, so that the creative designers may prepare in advance.