Strict Data Typing feature Macromedia introduced in Macromedia Flash MX 2004. Strict Data Typing allows us to explicitly declare the data type that a certain variable should accept, if the wrong data type is assigned to a variable an error message would pop up when the movie is tested identifying at what line exactly the wrong value was assigned to the variable. Strict Data Typing requires activation for each variable by using the : operator when the variable is declared.

 This is commen in most desktop languages. In flash strict data typing also has other gains. Strict data typing has some perfomance gain on lower spec hardware. Flash constantly checks what variable type a variable is when you change the contents of a variable. Using strict data typing allows flash to skip that operation because the player already knows what data type the variable should be. So use it from now on and enjoy an performace increase in your flash movies.