Regular Expressions 101

Save & Share

Flavor

  • PCRE2 (PHP >=7.3)
  • PCRE (PHP <7.3)
  • ECMAScript (JavaScript)
  • Python
  • Golang
  • Java 8
  • .NET 7.0 (C#)
  • Rust
  • Regex Flavor Guide

Function

  • Match
  • Substitution
  • List
  • Unit Tests

Tools

Sponsors
There are currently no sponsors. Become a sponsor today!
An explanation of your regex will be automatically generated as you type.
Detailed match information will be displayed here automatically.
  • All Tokens
  • Common Tokens
  • General Tokens
  • Anchors
  • Meta Sequences
  • Quantifiers
  • Group Constructs
  • Character Classes
  • Flags/Modifiers
  • Substitution
  • A single character of: a, b or c
    [abc]
  • A character except: a, b or c
    [^abc]
  • A character in the range: a-z
    [a-z]
  • A character not in the range: a-z
    [^a-z]
  • A character in the range: a-z or A-Z
    [a-zA-Z]
  • Any single character
    .
  • Alternate - match either a or b
    a|b
  • Any whitespace character
    \s
  • Any non-whitespace character
    \S
  • Any digit
    \d
  • Any non-digit
    \D
  • Any word character
    \w
  • Any non-word character
    \W
  • Non-capturing group
    (?:...)
  • Capturing group
    (...)
  • Zero or one of a
    a?
  • Zero or more of a
    a*
  • One or more of a
    a+
  • Exactly 3 of a
    a{3}
  • 3 or more of a
    a{3,}
  • Between 3 and 6 of a
    a{3,6}
  • Start of string
    ^
  • End of string
    $
  • A word boundary
    \b
  • Non-word boundary
    \B

Regular Expression
No Match

r"
"
gmx

Test String

Code Generator

Language

Generated Code

const regex = new RegExp('(?P<prop>[\\w-]+) # property name (?P<prop_params>; # property params, e.g. dstparams ( [\\w/,-]+(=[\\w/,-]+)?) # first param key[=val] element (;[\\w/,-]+(=[\\w/,-]+)?)* # additional key[=val] elements )?: # colon separator between prop and main params (?P<params> # main params ( [\\w/,-]+(=[\\w/,-]+)?) # first param key[=val] element (;[\\w/,-]+(=[\\w/,-]+)?)* # additional key[=val] elements )', 'gm') const str = `RRULE:FREQ=WEEKLY;UNTIL=20211231T183000Z;INTERVAL=1;BYDAY=TU,TH RRULE:FREQ=WEEKLY;WKST=SU;INTERVAL=4;BYDAY=FR RRULE:FREQ=DAILY;UNTIL=20150628;INTERVAL=3 RRULE:FREQ=DAILY;UNTIL=20150628 RRULE:FREQ=DAILY RRULE:ABC;DEF=GHI;jkl;abc=999 # negative example RRULE: # more examples DTSTART;TZID=America/New_York:19980101T090000 DTSTART;TZID=America/New_York:AB DTSTART;TZID=America;more;junk:AB=123;DE=456 DTSTART;TZID=America:AB DTSTART;junk:ABC=12333 RRULE:FREQ=YEARLY;BYMONTH=4;BYDAY=-1SU;UNTIL=19860427T070000Z DT;junk;more;junk=junk:ABC;YZO=123 RDATE;VALUE=DATE:20150609,20150611 EXDATE;VALUE=DATE:20150610 RDATE;TZID=America/New_York:19970714T083000 RDATE;VALUE=DATE:19970101,19970120,19970217,19970421 19970526,19970704,19970901,19971014,19971128,19971129,19971225 RRULE:FREQ=YEARLY;UNTIL=20000131T140000Z;BYMONTH=1;BYDAY=SU,MO,TU,WE,TH,FR,SA BEGIN:VTIMEZONE TZID:America/New_York LAST-MODIFIED:20050809T050000Z BEGIN:DAYLIGHT DTSTART:19670430T020000 RRULE:FREQ=YEARLY;BYMONTH=4;BYDAY=-1SU;UNTIL=19730429T070000Z TZOFFSETFROM:-0500 TZOFFSETTO:-0400 TZNAME:EDT END:DAYLIGHT BEGIN:STANDARD DTSTART:19671029T020000 RRULE:FREQ=YEARLY;BYMONTH=10;BYDAY=-1SU;UNTIL=20061029T060000Z TZOFFSETFROM:-0400 TZOFFSETTO:-0500 TZNAME:EST END:STANDARD BEGIN:DAYLIGHT DTSTART:19740106T020000 RDATE:19750223T020000 TZOFFSETFROM:-0500 TZOFFSETTO:-0400 TZNAME:EDT END:DAYLIGHT BEGIN:DAYLIGHT DTSTART:19760425T020000 RRULE:FREQ=YEARLY;BYMONTH=4;BYDAY=-1SU;UNTIL=19860427T070000Z TZOFFSETFROM:-0500 TZOFFSETTO:-0400 TZNAME:EDT END:DAYLIGHT BEGIN:DAYLIGHT DTSTART:19870405T020000 RRULE:FREQ=YEARLY;BYMONTH=4;BYDAY=1SU;UNTIL=20060402T070000Z TZOFFSETFROM:-0500 TZOFFSETTO:-0400 TZNAME:EDT END:DAYLIGHT BEGIN:DAYLIGHT DTSTART:20070311T020000 RRULE:FREQ=YEARLY;BYMONTH=3;BYDAY=2SU TZOFFSETFROM:-0500 TZOFFSETTO:-0400 TZNAME:EDT END:DAYLIGHT BEGIN:STANDARD DTSTART:20071104T020000 RRULE:FREQ=YEARLY;BYMONTH=11;BYDAY=1SU TZOFFSETFROM:-0400 TZOFFSETTO:-0500 TZNAME:EST END:STANDARD END:VTIMEZONE`; // Reset `lastIndex` if this regex is defined globally // regex.lastIndex = 0; let m; while ((m = regex.exec(str)) !== null) { // This is necessary to avoid infinite loops with zero-width matches if (m.index === regex.lastIndex) { regex.lastIndex++; } // The result can be accessed through the `m`-variable. m.forEach((match, groupIndex) => { console.log(`Found match, group ${groupIndex}: ${match}`); }); }

Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for JavaScript, please visit: https://developer.mozilla.org/en/docs/Web/JavaScript/Guide/Regular_Expressions