Regular Expressions \w knowledge of \d

After reviewing many of the relevant regular descriptions, it is found that the interpretation of \w refers to the inclusion of uppercase and lowercase alphanumeric and underscores equivalent ([0-9a-za-z]) (drawn from the Classic tutorial regular expression 30-minute introductory tutorial)

But in practice it is not true that this is not the case, it can be said that in fact not only contains ([0-9a-za-z_]) These data,

Here is the test tool for EditPlus:

The actual addition ([0-9a-za-z_]) also contains the Greek alphabet, Russian letters, etc.;

So if you need to pay attention to the specific matching data when registering the user information, you must not use \w directly.