Regular Expressions 101

^start of line

foothe literal text foo (case sensitive)

Negative Lookahead(?!.* ([abc]).*\1)

.*any Unicode character (except for line terminators), repeated any number of times

the literal (32₁₀ / 40₈ / 20₁₆)

Group 1([abc])

Character Class[abc]

athe literal a (97₁₀ / 141₈ / 61₁₆) (case sensitive)

bthe literal b (98₁₀ / 142₈ / 62₁₆) (case sensitive)

cthe literal c (99₁₀ / 143₈ / 63₁₆) (case sensitive)

.*any Unicode character (except for line terminators), repeated any number of times

\1the text saved by group 1

Non-Capturing Group(?: [abc])+

+repeats the group contents below at least once:

the literal (32₁₀ / 40₈ / 20₁₆)

Character Class[abc]

athe literal a (97₁₀ / 141₈ / 61₁₆) (case sensitive)

bthe literal b (98₁₀ / 142₈ / 62₁₆) (case sensitive)

cthe literal c (99₁₀ / 143₈ / 63₁₆) (case sensitive)

$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.

25 tokens

Regular Expression

^foo(?!.* ([abc]).*\1)(?: [abc])+$

New

foo a b c
foo b c a
foo a b
foo b
foo a b a

foo b b

foo a b c
foo b c a
foo a b
foo b
foo a b a

foo b b