When college acceptance letters are mailed out this month, tens of thousands of students will open a mixed bag.
They won’t be denied outright but instead relegated to the limbo known as a “wait list.”

The practice of wait listing—where colleges defer an admissions decision until accepted students have either taken or declined a spot in the freshman class—is essentially a school’s way of saying, “We like you, but we just can’t commit right now.”

Colleges often use a wait list to round out how their class looks. If there aren’t enough students in a certain major or from a particular region, the school will give wait-listed applicants who can help it meet those goals a higher priority. That makes it nearly impossible to predict your chances of getting off a wait list with any certainty, since it all depends on who applied in the first place, who chose to enroll, and how your characteristics compare to theirs.

Being wait listed is especially common for students applying to selective colleges, but some 550 colleges use them. More than 150,000 students accepted a spot on one in the fall of 2015.
Common as they are, however, wait lists remain one of the least transparent parts of the college admissions process. There are no rules for how many students can be put on a wait list, how long applicants can remain there, or even how long those who are accepted off the wait list have to decide whether they want to enroll.

Despite all that uncertainty, there are a few things you can control.