Regular Expressions 101

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/
magnet:\?.*?xt=urn:btih:([a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9])
/
gm
magnet:
matches the characters magnet: literally (case sensitive)
\? matches the character ? with index 6310 (3F16 or 778) literally (case sensitive)
.
matches any character (except for line terminators)
*? matches the previous token between zero and unlimited times, as few times as possible, expanding as needed (lazy)
xt=urn:btih:
matches the characters xt=urn:btih: literally (case sensitive)
1st Capturing Group
([a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9](?:\s*)[a-f0-9])
Match a single character present in the list below
[a-f0-9]
a-f matches a single character in the range between a (index 97) and f (index 102) (case sensitive)
0-9 matches a single character in the range between 0 (index 48) and 9 (index 57) (case sensitive)
Non-capturing group
(?:\s*)
\s
matches any whitespace character (equivalent to [\r\n\t\f\v ])
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
Match a single character present in the list below
[a-f0-9]
a-f matches a single character in the range between a (index 97) and f (index 102) (case sensitive)
0-9 matches a single character in the range between 0 (index 48) and 9 (index 57) (case sensitive)
Non-capturing group
(?:\s*)
\s
matches any whitespace character (equivalent to [\r\n\t\f\v ])
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
Match a single character present in the list below
[a-f0-9]
a-f matches a single character in the range between a (index 97) and f (index 102) (case sensitive)
0-9 matches a single character in the range between 0 (index 48) and 9 (index 57) (case sensitive)
Non-capturing group
(?:\s*)
\s
matches any whitespace character (equivalent to [\r\n\t\f\v ])
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
Match a single character present in the list below
[a-f0-9]
a-f matches a single character in the range between a (index 97) and f (index 102) (case sensitive)
0-9 matches a single character in the range between 0 (index 48) and 9 (index 57) (case sensitive)
Non-capturing group
(?:\s*)
\s
matches any whitespace character (equivalent to [\r\n\t\f\v ])
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
Match a single character present in the list below
[a-f0-9]
Non-capturing group
(?:\s*)
Match a single character present in the list below
[a-f0-9]
Non-capturing group
(?:\s*)
Match a single character present in the list below
[a-f0-9]
Non-capturing group
(?:\s*)
Match a single character present in the list below
[a-f0-9]
Non-capturing group
(?:\s*)
Match a single character present in the list below
[a-f0-9]
Non-capturing group
(?:\s*)
Match a single character present in the list below
[a-f0-9]
Non-capturing group
(?:\s*)
Match a single character present in the list below
[a-f0-9]
Non-capturing group
(?:\s*)
Match a single character present in the list below
[a-f0-9]
Non-capturing group
(?:\s*)
Match a single character present in the list below
[a-f0-9]
Non-capturing group
(?:\s*)
Match a single character present in the list below
[a-f0-9]
Non-capturing group
(?:\s*)
Match a single character present in the list below
[a-f0-9]
Non-capturing group
(?:\s*)
Match a single character present in the list below
[a-f0-9]
Non-capturing group
(?:\s*)
Match a single character present in the list below
[a-f0-9]
Non-capturing group
(?:\s*)
Match a single character present in the list below
[a-f0-9]
Non-capturing group
(?:\s*)
Match a single character present in the list below
[a-f0-9]
Non-capturing group
(?:\s*)
Match a single character present in the list below
[a-f0-9]
Non-capturing group
(?:\s*)
Match a single character present in the list below
[a-f0-9]
Non-capturing group
(?:\s*)
Match a single character present in the list below
[a-f0-9]
Non-capturing group
(?:\s*)
Match a single character present in the list below
[a-f0-9]
Non-capturing group
(?:\s*)
Match a single character present in the list below
[a-f0-9]
Non-capturing group
(?:\s*)
Match a single character present in the list below
[a-f0-9]
Non-capturing group
(?:\s*)
Match a single character present in the list below
[a-f0-9]
Non-capturing group
(?:\s*)
Match a single character present in the list below
[a-f0-9]
Non-capturing group
(?:\s*)
Match a single character present in the list below
[a-f0-9]
Non-capturing group
(?:\s*)
Match a single character present in the list below
[a-f0-9]
Non-capturing group
(?:\s*)
Match a single character present in the list below
[a-f0-9]
Non-capturing group
(?:\s*)
Match a single character present in the list below
[a-f0-9]
Non-capturing group
(?:\s*)
Match a single character present in the list below
[a-f0-9]
Non-capturing group
(?:\s*)
Match a single character present in the list below
[a-f0-9]
Non-capturing group
(?:\s*)
Match a single character present in the list below
[a-f0-9]
Non-capturing group
(?:\s*)
Match a single character present in the list below
[a-f0-9]
Non-capturing group
(?:\s*)
Match a single character present in the list below
[a-f0-9]
Non-capturing group
(?:\s*)
Match a single character present in the list below
[a-f0-9]
Non-capturing group
(?:\s*)
Match a single character present in the list below
[a-f0-9]
Non-capturing group
(?:\s*)
Match a single character present in the list below
[a-f0-9]
Non-capturing group
(?:\s*)
Match a single character present in the list below
[a-f0-9]
Global pattern flags
g modifier: global. All matches (don't return after first match)
m modifier: multi line. Causes ^ and $ to match the begin/end of each line (not only begin/end of string)
Your regular expression does not match the subject string.Try launching the debugger to find out why.

Regular Expression
No Match

/
/
gm

Test String