Below is a simple way to check if a string is null or empty in MS flow. It works by first testing if the string is null, and then checking if the string has 0 characters.


  • Add a condition step
  • Change the condition to OR
  • Add the string variable, and first test to see if it equals null
  • Secondly check if the formula length(<varaible>) is equal to 0

If the condition is true, your variable is null or empty