Also notepad++ can show white spaces chars including new lines which can be handy in such cases;it is probably the application or system you are using to view your file ignoring the linefeed not c# ignoring it

It makes minimal change to the text in particular it never splits a word doesn t change wc -w and for text with no more than single spaces in a row and no cr it doesn t change wc -c because it replaces spaces with linefeed rather than inserting linefeed

For example if i want to type this table character ascii tab 9 linefeed 10 carriage return 13 spaces 32 without using tabs i have to type spaces many times after the word tab not as many times after linefeed and only a few times after carriage return

This regex does replace by a single spaces all contiguous spaces 2 or more followed by a linefeed or individual tabs

S will match more than just spaces because this also matches vertical whitespaces like linefeed carriage returns.

Syntax notation the following core rules are included by reference as defined in rfc5234 appendix b.1 alpha letters cr carriage return crlf cr linefeed ctl controls digit decimal 0-9 dquote double quote hexdig hexadecimal 0-9 a-f a-f htab horizontal tab linefeed linefeed octet any 8-bit sequence of data sp spaces and vchar any visible usascii character . so whitespace is not allowed in the name of a header;spaces is not a valid character in a header name