How to find out if string has already been URL encoded?

Question

How could I check if string has already been encoded?

For example, if I encode TEST==, I get TEST%3D%3D. If I again encode last string, I

Answer 1

If you want to be sure that string is encoded correctly (if it needs to be encoded) - just decode and encode it once again.

metacode:

100%_correctly_encoded_string = encode(decode(input_string))

already encoded string will remain untouched. Unencoded string will be encoded. String with only url-allowed characters will remain untouched too.