Regular Expressions 101

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/
rgba?\(\s*(25[0-5]|2[0-4]\d|1\d{1,2}|\d\d?)\s*,\s*(25[0-5]|2[0-4]\d|1\d{1,2}|\d\d?)\s*,\s*(25[0-5]|2[0-4]\d|1\d{1,2}|\d\d?)\s*,?\s*([01\.]\.?\d?)?\s*\)
/
gm
rgb
matches the characters rgb literally (case sensitive)
a
matches the character a with index 9710 (6116 or 1418) literally (case sensitive)
\( matches the character ( with index 4010 (2816 or 508) literally (case sensitive)
\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)
1st Capturing Group
(25[0-5]|2[0-4]\d|1\d{1,2}|\d\d?)
1st Alternative
25[0-5]
25
matches the characters 25 literally (case sensitive)
Match a single character present in the list below
[0-5]
0-5 matches a single character in the range between 0 (index 48) and 5 (index 53) (case sensitive)
2nd Alternative
2[0-4]\d
2 matches the character 2 with index 5010 (3216 or 628) literally (case sensitive)
Match a single character present in the list below
[0-4]
0-4 matches a single character in the range between 0 (index 48) and 4 (index 52) (case sensitive)
\d matches a digit (equivalent to [0-9])
3rd Alternative
1\d{1,2}
1 matches the character 1 with index 4910 (3116 or 618) literally (case sensitive)
\d
matches a digit (equivalent to [0-9])
{1,2} matches the previous token between 1 and 2 times, as many times as possible, giving back as needed (greedy)
4th Alternative
\d\d?
\d matches a digit (equivalent to [0-9])
\d
matches a digit (equivalent to [0-9])
? matches the previous token between zero and one times, as many times as possible, giving back as needed (greedy)
\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)
, matches the character , with index 4410 (2C16 or 548) literally (case sensitive)
\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)
2nd Capturing Group
(25[0-5]|2[0-4]\d|1\d{1,2}|\d\d?)
1st Alternative
25[0-5]
25
matches the characters 25 literally (case sensitive)
Match a single character present in the list below
[0-5]
0-5 matches a single character in the range between 0 (index 48) and 5 (index 53) (case sensitive)
2nd Alternative
2[0-4]\d
2 matches the character 2 with index 5010 (3216 or 628) literally (case sensitive)
Match a single character present in the list below
[0-4]
0-4 matches a single character in the range between 0 (index 48) and 4 (index 52) (case sensitive)
\d matches a digit (equivalent to [0-9])
3rd Alternative
1\d{1,2}
1 matches the character 1 with index 4910 (3116 or 618) literally (case sensitive)
\d
matches a digit (equivalent to [0-9])
{1,2} matches the previous token between 1 and 2 times, as many times as possible, giving back as needed (greedy)
4th Alternative
\d\d?
\d matches a digit (equivalent to [0-9])
\d
matches a digit (equivalent to [0-9])
? matches the previous token between zero and one times, as many times as possible, giving back as needed (greedy)
\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)
, matches the character , with index 4410 (2C16 or 548) literally (case sensitive)
\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)
3rd Capturing Group
(25[0-5]|2[0-4]\d|1\d{1,2}|\d\d?)
1st Alternative
25[0-5]
25
matches the characters 25 literally (case sensitive)
Match a single character present in the list below
[0-5]
0-5 matches a single character in the range between 0 (index 48) and 5 (index 53) (case sensitive)
2nd Alternative
2[0-4]\d
2 matches the character 2 with index 5010 (3216 or 628) literally (case sensitive)
Match a single character present in the list below
[0-4]
0-4 matches a single character in the range between 0 (index 48) and 4 (index 52) (case sensitive)
\d matches a digit (equivalent to [0-9])
3rd Alternative
1\d{1,2}
4th Alternative
\d\d?
\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)
,
matches the character , with index 4410 (2C16 or 548) literally (case sensitive)
\s
matches any whitespace character (equivalent to [\r\n\t\f\v ])
4th Capturing Group
([01\.]\.?\d?)?
\s
matches any whitespace character (equivalent to [\r\n\t\f\v ])
\) matches the character ) with index 4110 (2916 or 518) literally (case sensitive)
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