Regular Expressions 101

^start of line

Positive Lookahead(?=[a-zA-Z]{7}$)

Character Class[a-zA-Z]{7}

{7}matches exactly 7 characters from the set below:

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

A-Zone character from A (65₁₀) to Z (90₁₀) (case sensitive)

$end of line

Group 1(.)

.any character (except for line terminators)

Negative Lookahead(?!\1)

\1the text saved by group 1

Group 2(.)

.any character (except for line terminators)

Negative Lookahead(?!\1)

\1the text saved by group 1

Negative Lookahead(?!\2)

\2the text saved by group 2

Group 3(.)

.any character (except for line terminators)

\2the text saved by group 2

Negative Lookahead(?!\1)

\1the text saved by group 1

Negative Lookahead(?!\2)

\2the text saved by group 2

Negative Lookahead(?!\3)

\3the text saved by group 3

.any character (except for line terminators)

\2the text saved by group 2

\1the text saved by group 1

$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-zA-Z]{7}$)(.)(?!\1)(.)(?!\1)(?!\2)(.)\2(?!\1)(?!\2)(?!\3).\2\1$

New

abcbdba
aaaaaaa
abcdefg
abababa