RewriteRule - Caret ^ - Match

Question

I am confused about this rule:

RewriteCond %{HTTPS} !=on

RewriteRule ^ https://%{HTTP_HOST}%{REQUEST_URI} [L,R=301,QSA]

How is it possible that a caret can match the whole URL if it is a position anchor?

I cannot find any official statement that it is a catch all symbol.

Answer 1

The caret means looking at the beginning of a line.

The caret matches at the beginning without consuming a character. So even the empty string matches ^. The empty string also matches ^$ since it begins at index 0 and ends at index 0.

The caret matches because the regular expression only needs to be found somewhere in the URL. It doesn't need to match the whole URL.

Using exactly ^ as the regular expression allows for more performance, since typical regular expressions only compare the beginning of the URL and therefore don't need to look at every character of the URL.