Regular Expressions 101

^start of line

Character Class[a-z]

a-zone character from a (97₁₀) to z (122₁₀) (case sensitive)

Positive Lookahead(?=(?:[a-z]*\d){0,4}(?![a-z]*\d))

Non-Capturing Group(?:[a-z]*\d){0,4}

{0,4}repeats the group contents below between 0 and 4 times:

Character Class[a-z]*

*matches any number of characters from the set below:

a-zone character from a (97₁₀) to z (122₁₀) (case sensitive)

\da digit

Negative Lookahead(?![a-z]*\d)

Character Class[a-z]*

*matches any number of characters from the set below:

a-zone character from a (97₁₀) to z (122₁₀) (case sensitive)

\da digit

Positive Lookahead(?=[a-z\d]{3,11}$)

Character Class[a-z\d]{3,11}

{3,11}matches between 3 and 11 characters from the set below:

a-zone character from a (97₁₀) to z (122₁₀) (case sensitive)

\da digit

$end of line

Character Class[a-z\d]+

+matches at least one character from the set below:

a-zone character from a (97₁₀) to z (122₁₀) (case sensitive)

\da digit

$end of line

Global pattern flags

g modifier: global. Finds all matches instead of stopping after the first

m modifier: multiline. Causes ^ and $ to match the start and end of each line, not only the start and end of the string

Detailed match information will be displayed here automatically.

Search reference

Regular Expression

^[a-z](?=(?:[a-z]*\d){0,4}(?![a-z]*\d))(?=[a-z\d]{3,11}$)[a-z\d]+$

New

a1a2a3a4aaaa
a3333aaaaaaa
a1a2a3aaaaa2
a1a2a3
a222
aaaa
a2aa
f2fdfgdd
w333rrrrrrr4
rrrrrrrr4444
r22rrrrrrrrr
g4fff333ffff

333333333333
1111
1aaa
1aaaaaaaaaaa
1a2aaaaaaaaa
a1aaaaaaaaaaa
a11111aaaaaa
a122a3aaaaa2
a1a2a3a4a5aa

Regular Expression

Extraction