Regular Expressions 101

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/
^((([A-Za-z][A-Za-z0-9]*[\.\_]*[A-Za-z0-9]+){0,30}@[a-z]{3,15}\.[a-z]{2,5})|(([A-Za-z][A-Za-z0-9]*[._]*[A-Za-z0-9]+){0,30}@[a-z]{3,15}\.[a-z]{2}\.[a-z]{2,5}))$
/
^ asserts position at start of the string
1st Capturing Group
((([A-Za-z][A-Za-z0-9]*[\.\_]*[A-Za-z0-9]+){0,30}@[a-z]{3,15}\.[a-z]{2,5})|(([A-Za-z][A-Za-z0-9]*[._]*[A-Za-z0-9]+){0,30}@[a-z]{3,15}\.[a-z]{2}\.[a-z]{2,5}))
1st Alternative
(([A-Za-z][A-Za-z0-9]*[\.\_]*[A-Za-z0-9]+){0,30}@[a-z]{3,15}\.[a-z]{2,5})
2nd Capturing Group
(([A-Za-z][A-Za-z0-9]*[\.\_]*[A-Za-z0-9]+){0,30}@[a-z]{3,15}\.[a-z]{2,5})
3rd Capturing Group
([A-Za-z][A-Za-z0-9]*[\.\_]*[A-Za-z0-9]+){0,30}
{0,30} matches the previous token between 0 and 30 times, as many times as possible, giving back as needed (greedy)
A repeated capturing group will only capture the last iteration. Put a capturing group around the repeated group to capture all iterations or use a non-capturing group instead if you're not interested in the data
Match a single character present in the list below
[A-Za-z]
A-Z matches a single character in the range between A (index 65) and Z (index 90) (case sensitive)
a-z matches a single character in the range between a (index 97) and z (index 122) (case sensitive)
Match a single character present in the list below
[A-Za-z0-9]
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
A-Z matches a single character in the range between A (index 65) and Z (index 90) (case sensitive)
a-z matches a single character in the range between a (index 97) and z (index 122) (case sensitive)
0-9 matches a single character in the range between 0 (index 48) and 9 (index 57) (case sensitive)
Match a single character present in the list below
[\.\_]
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
\. matches the character . with index 4610 (2E16 or 568) literally (case sensitive)
\_ matches the character _ with index 9510 (5F16 or 1378) literally (case sensitive)
Match a single character present in the list below
[A-Za-z0-9]
+ matches the previous token between one and unlimited times, as many times as possible, giving back as needed (greedy)
A-Z matches a single character in the range between A (index 65) and Z (index 90) (case sensitive)
a-z matches a single character in the range between a (index 97) and z (index 122) (case sensitive)
0-9 matches a single character in the range between 0 (index 48) and 9 (index 57) (case sensitive)
@ matches the character @ with index 6410 (4016 or 1008) literally (case sensitive)
Match a single character present in the list below
[a-z]
{3,15} matches the previous token between 3 and 15 times, as many times as possible, giving back as needed (greedy)
a-z matches a single character in the range between a (index 97) and z (index 122) (case sensitive)
\. matches the character . with index 4610 (2E16 or 568) literally (case sensitive)
Match a single character present in the list below
[a-z]
{2,5} matches the previous token between 2 and 5 times, as many times as possible, giving back as needed (greedy)
a-z matches a single character in the range between a (index 97) and z (index 122) (case sensitive)
2nd Alternative
(([A-Za-z][A-Za-z0-9]*[._]*[A-Za-z0-9]+){0,30}@[a-z]{3,15}\.[a-z]{2}\.[a-z]{2,5})
4th Capturing Group
(([A-Za-z][A-Za-z0-9]*[._]*[A-Za-z0-9]+){0,30}@[a-z]{3,15}\.[a-z]{2}\.[a-z]{2,5})
5th Capturing Group
([A-Za-z][A-Za-z0-9]*[._]*[A-Za-z0-9]+){0,30}
{0,30} matches the previous token between 0 and 30 times, as many times as possible, giving back as needed (greedy)
A repeated capturing group will only capture the last iteration. Put a capturing group around the repeated group to capture all iterations or use a non-capturing group instead if you're not interested in the data
Match a single character present in the list below
[A-Za-z]
A-Z matches a single character in the range between A (index 65) and Z (index 90) (case sensitive)
a-z matches a single character in the range between a (index 97) and z (index 122) (case sensitive)
Match a single character present in the list below
[A-Za-z0-9]
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
A-Z matches a single character in the range between A (index 65) and Z (index 90) (case sensitive)
a-z matches a single character in the range between a (index 97) and z (index 122) (case sensitive)
0-9 matches a single character in the range between 0 (index 48) and 9 (index 57) (case sensitive)
Match a single character present in the list below
[._]
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
._
matches a single character in the list ._ (case sensitive)
Match a single character present in the list below
[A-Za-z0-9]
+ matches the previous token between one and unlimited times, as many times as possible, giving back as needed (greedy)
A-Z matches a single character in the range between A (index 65) and Z (index 90) (case sensitive)
a-z matches a single character in the range between a (index 97) and z (index 122) (case sensitive)
0-9 matches a single character in the range between 0 (index 48) and 9 (index 57) (case sensitive)
@ matches the character @ with index 6410 (4016 or 1008) literally (case sensitive)
Match a single character present in the list below
[a-z]
{3,15} matches the previous token between 3 and 15 times, as many times as possible, giving back as needed (greedy)
a-z matches a single character in the range between a (index 97) and z (index 122) (case sensitive)
\. matches the character . with index 4610 (2E16 or 568) literally (case sensitive)
Match a single character present in the list below
[a-z]
{2} matches the previous token exactly 2 times
a-z matches a single character in the range between a (index 97) and z (index 122) (case sensitive)
\. matches the character . with index 4610 (2E16 or 568) literally (case sensitive)
Match a single character present in the list below
[a-z]
{2,5} matches the previous token between 2 and 5 times, as many times as possible, giving back as needed (greedy)
a-z matches a single character in the range between a (index 97) and z (index 122) (case sensitive)
$ asserts position at the end of the string
Your regular expression does not match the subject string.

Regular Expression
No Match

/
/

Test String

Substitution

Processing...