Regular Expressions 101

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/
https?:\/\/(?:www.)?instagram.com\/reel\/([^\/?#&]+).*
/
gm
http
matches the characters http 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)
Non-capturing group
(?:www.)?
? matches the previous token between zero and one times, as many times as possible, giving back as needed (greedy)
www
matches the characters www literally (case sensitive)
. matches any character (except for line terminators)
instagram
matches the characters instagram literally (case sensitive)
. matches any character (except for line terminators)
com
matches the characters com literally (case sensitive)
\/ matches the character / with index 4710 (2F16 or 578) literally (case sensitive)
reel
matches the characters reel literally (case sensitive)
\/ matches the character / with index 4710 (2F16 or 578) literally (case sensitive)
1st Capturing Group
([^\/?#&]+)
Match a single character not present in the list below
[^\/?#&]
+ 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 a single character in the list ?#& (case sensitive)
.
matches any character (except for line terminators)
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
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