Hi Joseph!
Thanks for your question and Happy New Year!
This was such an easy question to answer 5-10 years ago when there were very distinct "seasons" at
Walt Disney World Resort. However, as the property has expanded over the years and added more to the parks, more resorts and more to
Disney Springs and
ESPN Wide World of Sports Complex, there are very few "slow" times of year any longer.
That said, there are still a few "sweet spots" to visit, as I like to call them.
Please keep in mind that this is neither a comprehensive list nor times when the parks are empty, but they are simply times when the parks and resorts are historically less crowded. Mid January to mid-February (except February School Break week for the Northeast), late February to mid-March (before Spring Break season), late August, most of September (due to kids back in school), most weekdays in October, most of November (except Thanksgiving week), and the days between Thanksgiving and Christmas.
I hope this helps and I wish you a Magical and crowd lessened trip!!
Chris