Preheat oven to 350°F (175°C).
Mix crushed pretzels, melted butter, and sugar. Press firmly into a 9x13-inch baking dish.
Bake for 10 minutes, then cool completely.
Beat cream cheese and sugar until smooth. Fold in whipped topping.
Spread cream cheese mixture evenly over cooled crust, sealing edges.
Refrigerate 30 minutes.
Dissolve Jell-O in boiling water. Let cool until slightly thickened but not set.
Arrange sliced strawberries over cream cheese layer.
Carefully pour cooled Jell-O over strawberries.
Refrigerate 3–4 hours, or until fully set.