Regular Expressions 101

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/
^(?:http|ftp)s?:\/\/([\w][^\/=\s]+)\/?|(^w{3}[\.\w][^\/\=\s]{2,})\/?
/
mg
1st Alternative
^(?:http|ftp)s?:\/\/([\w][^\/=\s]+)\/?
^ asserts position at start of a line
Non-capturing group
(?:http|ftp)
1st Alternative
http
http
matches the characters http literally (case sensitive)
2nd Alternative
ftp
ftp
matches the characters ftp literally (case sensitive)
s
matches the character s with index 11510 (7316 or 1638) literally (case sensitive)
: matches the character : with index 5810 (3A16 or 728) literally (case sensitive)
\/ matches the character / with index 4710 (2F16 or 578) literally (case sensitive)
\/ matches the character / with index 4710 (2F16 or 578) literally (case sensitive)
1st Capturing Group
([\w][^\/=\s]+)
Match a single character present in the list below
[\w]
\w matches any word character (equivalent to [a-zA-Z0-9_])
Match a single character not present in the list below
[^\/=\s]
+ matches the previous token between one and unlimited times, as many times as possible, giving back as needed (greedy)
\/ matches the character / with index 4710 (2F16 or 578) literally (case sensitive)
= matches the character = with index 6110 (3D16 or 758) literally (case sensitive)
\s matches any whitespace character (equivalent to [\r\n\t\f\v ])
\/
matches the character / with index 4710 (2F16 or 578) literally (case sensitive)
? matches the previous token between zero and one times, as many times as possible, giving back as needed (greedy)
2nd Alternative
(^w{3}[\.\w][^\/\=\s]{2,})\/?
2nd Capturing Group
(^w{3}[\.\w][^\/\=\s]{2,})
^ asserts position at start of a line
w
matches the character w with index 11910 (7716 or 1678) literally (case sensitive)
Match a single character present in the list below
[\.\w]
\. matches the character . with index 4610 (2E16 or 568) literally (case sensitive)
\w matches any word character (equivalent to [a-zA-Z0-9_])
Match a single character not present in the list below
[^\/\=\s]
{2,} matches the previous token between 2 and unlimited times, as many times as possible, giving back as needed (greedy)
\/ matches the character / with index 4710 (2F16 or 578) literally (case sensitive)
\= matches the character = with index 6110 (3D16 or 758) literally (case sensitive)
\s matches any whitespace character (equivalent to [\r\n\t\f\v ])
\/
matches the character / with index 4710 (2F16 or 578) literally (case sensitive)
? matches the previous token between zero and one times, as many times as possible, giving back as needed (greedy)
Global pattern flags
m modifier: multi line. Causes ^ and $ to match the begin/end of each line (not only begin/end of string)
g modifier: global. All matches (don't return after first match)
Your regular expression does not match the subject string.Try launching the debugger to find out why.

Regular Expression
No Match

/
/
mg

Test String