Pay-on-win
This is the standard contest model, where the contest holder pays the designer if they declare a winner. Contest holders have the option of withdrawing the contest if they don't find a result they are happy with.
The standard contest length is 7 days, after which the contest holder either awards a prize or withdraws the contest.
Private
Private contests are only visible to people logged in to 99designs. They are not included in the site search or feeds, and are hidden from other search engines such as Google.
Designs submitted to private contests may not be added to designer folios, and do not appear on designers profile page unless negotiated otherwise.
Because of this, higher prize amounts are encouraged for Private Contests.
Fast Track
Fast-tracked contests run for a shorter period of time, ranging between 1-3 days. These contests are run by contest holders who want results fast, and generally have a higher prize. Contest holders are expected to be more responsive with feedback in these contests.
Contest holders can purchase an upgrade during the launch process to create a fast-tracked contest.
Guaranteed
Guaranteed contests are contests where the contest holder has guaranteed that a winner will be chosen and that the prize money will be awarded. These contests have had the prize money pre-paid to 99designs, who will award the prize to the winning designer at the end of the contest.
This contest type is the safest bet for designers to enter, and tends to encourage the most designers and best quality work.
At present this feature is being trialed on-request only, contact sales@99designs.com for more details.