Regular Expressions 101

Save & Share

  • Save Regex
    ctrl+s
  • Update Regex
    ctrl+⇧+s

Flavor

  • PCRE2 (PHP >=7.3)
  • PCRE (PHP <7.3)
  • ECMAScript (JavaScript)
  • Python
  • Golang
  • Java 8

Function

  • Match
  • Substitution
  • List
  • Unit Tests
/
(\w)(\w)\1(.*)\2\1\2
/
g
1st Capturing Group
(\w)
\w matches any word character (equivalent to [a-zA-Z0-9_])
2nd Capturing Group
(\w)
\w matches any word character (equivalent to [a-zA-Z0-9_])
\1 matches the same text as most recently matched by the 1st capturing group
3rd Capturing Group
(.*)
.
matches any character (except for line terminators)
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
\2 matches the same text as most recently matched by the 2nd capturing group
\1 matches the same text as most recently matched by the 1st capturing group
\2 matches the same text as most recently matched by the 2nd capturing group
Global pattern flags
g modifier: global. All matches (don't return after first match)
Your regular expression does not match the subject string.Try launching the debugger to find out why.

Regular Expression
No Match

/
/
g

Test String