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

/
/
gm

Test String

Code Generator

Language

Generated Code

import java.util.regex.Matcher; import java.util.regex.Pattern; public class Example { public static void main(String[] args) { final String regex = "(?=(?:^(?:\\d\\d\\d\\d-(?:0[1-9]|10|11|12)-(?:0[1-9]|1[0-9]|2[0-8])|\\d\\d\\d\\d-(?:0[13-9]|10|11|12)-(?:29|30)|\\d\\d\\d\\d-(?:0[13578]|10|12)-31|(?:\\d\\d[2468][048]|\\d\\d0[48]|\\d\\d[13579][26])-02-29|(?:[02468][048]00|[13579][26]00)-02-29)T(?:(?:0[0-9]|1[0-9]|2[0-3]):(?:[0-5][0-9]):(?:[0-5][0-9]))(?:\\.\\d\\d\\d)?(?:Z|[\\+\\-](?:0[0-9]|1[012]):00|\\+0[34569]:30|\\+10:30|-0[39]:30|\\+1[34]:00|\\+0[58]:45|\\+12:45)$)|^(?:1972|198[1235]|199[2347]|2012|2015)-06-30T23:59:60Z$|^(?:197[2-9]|1987|1989|199[058]|2005|2008|2016)-12-31T23:59:60Z$)(?!.*-00:00$)^(\\d\\d\\d\\d)-(\\d\\d)-(\\d\\d)T(\\d\\d):(\\d\\d):(\\d\\d)(?:\\.(\\d\\d\\d))?((Z)|([\\+\\-])(\\d\\d):(\\d\\d))$"; final String string = "Strong Matcher for ISO 8601 / RFC 3339 Date Times; rejects bad TZ offsets, illegal times (Museum of Bad Data)\n" + "See below for expanded matcher\n\n" + "```\n" + "// accept: Exemplars\n" + "2008-02-03T04:05:06.007Z\n" + "2008-02-03T04:05:06Z\n" + "0000-01-01T00:00:00.000Z\n" + "0000-02-29T04:05:06.007Z\n" + "9999-12-31T23:59:59.999Z\n" + "9999-12-31T23:59:59Z\n" + "2008-02-03T04:05:06.007+12:45\n" + "2008-02-03T04:05:06+03:30\n" + "0000-01-01T00:00:00.007-09:30\n" + "0000-02-29T04:05:06.007+14:00\n" + "9999-12-31T23:59:59.999+12:00\n" + "9999-12-31T23:59:59-12:00\n" + "// accept: Leap day, year is multiple of four\n" + "0004-02-29T04:05:06.007Z\n" + "0008-02-29T04:05:06.007Z\n" + "0012-02-29T04:05:06.007Z\n" + "0016-02-29T04:05:06.007Z\n" + "0020-02-29T04:05:06.007Z\n" + "0024-02-29T04:05:06.007Z\n" + "0028-02-29T04:05:06.007Z\n" + "0032-02-29T04:05:06.007Z\n" + "0036-02-29T04:05:06.007Z\n" + "0040-02-29T04:05:06.007Z\n" + "0044-02-29T04:05:06.007Z\n" + "0048-02-29T04:05:06.007Z\n" + "0052-02-29T04:05:06.007Z\n" + "0056-02-29T04:05:06.007Z\n" + "0060-02-29T04:05:06.007Z\n" + "0064-02-29T04:05:06.007Z\n" + "0068-02-29T04:05:06.007Z\n" + "0072-02-29T04:05:06.007Z\n" + "0076-02-29T04:05:06.007Z\n" + "0080-02-29T04:05:06.007Z\n" + "0084-02-29T04:05:06.007Z\n" + "0088-02-29T04:05:06.007Z\n" + "0092-02-29T04:05:06.007Z\n" + "0096-02-29T04:05:06.007Z\n" + "1560-02-29T04:05:06.007Z\n" + "2004-02-29T04:05:06.007Z\n" + "2008-02-29T04:05:06.007Z\n" + "2012-02-29T04:05:06.007Z\n" + "2016-02-29T04:05:06.007Z\n" + "2020-02-29T04:05:06.007Z\n" + "2024-02-29T04:05:06.007Z\n" + "2028-02-29T04:05:06.007Z\n" + "2032-02-29T04:05:06.007Z\n" + "2036-02-29T04:05:06.007Z\n" + "2040-02-29T04:05:06.007Z\n" + "2044-02-29T04:05:06.007Z\n" + "9996-02-29T04:05:06.007Z\n" + "// accept: Leap day, year is Multiple of 400\n" + "0000-02-29T04:05:06.007Z\n" + "0400-02-29T04:05:06.007Z\n" + "0800-02-29T04:05:06.007Z\n" + "1200-02-29T04:05:06.007Z\n" + "1600-02-29T04:05:06.007Z\n" + "2000-02-29T04:05:06.007Z\n" + "2400-02-29T04:05:06.007Z\n" + "2800-02-29T04:05:06.007Z\n" + "3200-02-29T04:05:06.007Z\n" + "3600-02-29T04:05:06.007Z\n" + "4000-02-29T04:05:06.007Z\n" + "4400-02-29T04:05:06.007Z\n" + "4800-02-29T04:05:06.007Z\n" + "5200-02-29T04:05:06.007Z\n" + "5600-02-29T04:05:06.007Z\n" + "6000-02-29T04:05:06.007Z\n" + "6400-02-29T04:05:06.007Z\n" + "6800-02-29T04:05:06.007Z\n" + "7200-02-29T04:05:06.007Z\n" + "7600-02-29T04:05:06.007Z\n" + "8000-02-29T04:05:06.007Z\n" + "8400-02-29T04:05:06.007Z\n" + "8800-02-29T04:05:06.007Z\n" + "9200-02-29T04:05:06.007Z\n" + "9600-02-29T04:05:06.007Z\n" + "// accept: Day in range for month\n" + "2008-01-30T04:05:06.007Z\n" + "2008-03-30T04:05:06.007Z\n" + "2008-04-30T04:05:06.007Z\n" + "2008-05-30T04:05:06.007Z\n" + "2008-06-30T04:05:06.007Z\n" + "2008-07-30T04:05:06.007Z\n" + "2008-08-30T04:05:06.007Z\n" + "2008-09-30T04:05:06.007Z\n" + "2008-10-30T04:05:06.007Z\n" + "2008-11-30T04:05:06.007Z\n" + "2008-12-30T04:05:06.007Z\n" + "2008-01-31T04:05:06.007Z\n" + "2008-03-31T04:05:06.007Z\n" + "2008-05-31T04:05:06.007Z\n" + "2008-07-31T04:05:06.007Z\n" + "2008-08-31T04:05:06.007Z\n" + "2008-10-31T04:05:06.007Z\n" + "2008-12-31T04:05:06.007Z\n" + "// accept: had leap second\n" + "1972-06-30T23:59:60Z\n" + "1981-06-30T23:59:60Z\n" + "1982-06-30T23:59:60Z\n" + "1983-06-30T23:59:60Z\n" + "1985-06-30T23:59:60Z\n" + "1992-06-30T23:59:60Z\n" + "1993-06-30T23:59:60Z\n" + "1994-06-30T23:59:60Z\n" + "1997-06-30T23:59:60Z\n" + "2012-06-30T23:59:60Z\n" + "2015-06-30T23:59:60Z\n" + "1972-12-31T23:59:60Z\n" + "1973-12-31T23:59:60Z\n" + "1974-12-31T23:59:60Z\n" + "1975-12-31T23:59:60Z\n" + "1976-12-31T23:59:60Z\n" + "1977-12-31T23:59:60Z\n" + "1978-12-31T23:59:60Z\n" + "1979-12-31T23:59:60Z\n" + "1987-12-31T23:59:60Z\n" + "1989-12-31T23:59:60Z\n" + "1990-12-31T23:59:60Z\n" + "1995-12-31T23:59:60Z\n" + "1998-12-31T23:59:60Z\n" + "2005-12-31T23:59:60Z\n" + "2008-12-31T23:59:60Z\n" + "2016-12-31T23:59:60Z\n" + "// REJECT: Year out of range\n" + "10000-02-29T04:05:06.007Z\n" + "// REJECT: Month out of range\n" + "2008-00-30T04:05:06.007Z\n" + "2008-13-30T04:05:06.007Z\n" + "2008-14-30T04:05:06.007Z\n" + "2008-20-30T04:05:06.007Z\n" + "// REJECT: Day out of range for month\n" + "2008-02-30T04:05:06.007Z\n" + "2008-04-31T04:05:06.007Z\n" + "2008-06-31T04:05:06.007Z\n" + "2008-09-31T04:05:06.007Z\n" + "2008-11-31T04:05:06.007Z\n" + "2008-02-31T04:05:06.007Z\n" + "// REJECT: Day out of range\n" + "2008-12-32T04:05:06.007Z\n" + "2008-12-99T04:05:06.007Z\n" + "2008-12-00T04:05:06.007Z\n" + "// REJECT: Hour out of range\n" + "2008-12-08T60:05:06.007Z\n" + "2008-12-08T99:05:06.007Z\n" + "// REJECT: Minute out of range\n" + "2008-12-08T04:60:06.007Z\n" + "2008-12-08T04:99:06.007Z\n" + "// REJECT: Seconds out of range\n" + "9999-12-31T59:59:61.999Z\n" + "2008-02-03T04:05:61.999Z\n" + "2008-02-03T04:05:61Z\n" + "// REJECT: Negative dates not accepted\n" + "-2000-02-29T04:05:06.007Z\n" + "-0400-02-29T04:05:06.007Z\n" + "-0100-02-29T04:05:06.007Z\n" + "-0004-02-29T04:05:06.007Z\n" + "// REJECT: stray characters\n" + " 2008-12-31T04:05:06.007Z\n" + "2008-12-31T04:05:06.007Z \n" + "2008-12-31T04:05:06.007 Z\n" + "// REJECT: Malformed\n" + "2008-02-0304:05:06.007Z\n" + "20080203T040506.007Z\n" + "2008-02-03T04:05:06007Z\n" + "2008-02-03T04:05:06.7Z\n" + "2008-02-03T04:05:06.07Z\n" + "2008-02-03T04:05:06.0007Z\n" + "2008-02-03T04:05:06\n" + "2008-02-03T04:05:06.Z\n" + "// REJECT: no leap second\n" + "1973-06-30T23:59:60Z\n" + "1974-06-30T23:59:60Z\n" + "1975-06-30T23:59:60Z\n" + "1976-06-30T23:59:60Z\n" + "1977-06-30T23:59:60Z\n" + "1978-06-30T23:59:60Z\n" + "1979-06-30T23:59:60Z\n" + "1980-06-30T23:59:60Z\n" + "1984-06-30T23:59:60Z\n" + "1986-06-30T23:59:60Z\n" + "1987-06-30T23:59:60Z\n" + "1988-06-30T23:59:60Z\n" + "1989-06-30T23:59:60Z\n" + "1990-06-30T23:59:60Z\n" + "1991-06-30T23:59:60Z\n" + "1995-06-30T23:59:60Z\n" + "1996-06-30T23:59:60Z\n" + "1998-06-30T23:59:60Z\n" + "1999-06-30T23:59:60Z\n" + "2000-06-30T23:59:60Z\n" + "2001-06-30T23:59:60Z\n" + "2002-06-30T23:59:60Z\n" + "2003-06-30T23:59:60Z\n" + "2004-06-30T23:59:60Z\n" + "2005-06-30T23:59:60Z\n" + "2006-06-30T23:59:60Z\n" + "2007-06-30T23:59:60Z\n" + "2008-06-30T23:59:60Z\n" + "2009-06-30T23:59:60Z\n" + "2010-06-30T23:59:60Z\n" + "2011-06-30T23:59:60Z\n" + "2013-06-30T23:59:60Z\n" + "2014-06-30T23:59:60Z\n" + "2016-06-30T23:59:60Z\n" + "2017-06-30T23:59:60Z\n" + "2018-06-30T23:59:60Z\n" + "2019-06-30T23:59:60Z\n" + "2020-06-30T23:59:60Z\n" + "2021-06-30T23:59:60Z\n" + "2022-06-30T23:59:60Z\n" + "2023-06-30T23:59:60Z\n" + "1980-12-31T23:59:60Z\n" + "1981-12-31T23:59:60Z\n" + "1982-12-31T23:59:60Z\n" + "1983-12-31T23:59:60Z\n" + "1984-12-31T23:59:60Z\n" + "1985-12-31T23:59:60Z\n" + "1986-12-31T23:59:60Z\n" + "1988-12-31T23:59:60Z\n" + "1991-12-31T23:59:60Z\n" + "1992-12-31T23:59:60Z\n" + "1993-12-31T23:59:60Z\n" + "1994-12-31T23:59:60Z\n" + "1996-12-31T23:59:60Z\n" + "1997-12-31T23:59:60Z\n" + "1999-12-31T23:59:60Z\n" + "2000-12-31T23:59:60Z\n" + "2001-12-31T23:59:60Z\n" + "2002-12-31T23:59:60Z\n" + "2003-12-31T23:59:60Z\n" + "2004-12-31T23:59:60Z\n" + "2006-12-31T23:59:60Z\n" + "2007-12-31T23:59:60Z\n" + "2009-12-31T23:59:60Z\n" + "2010-12-31T23:59:60Z\n" + "2011-12-31T23:59:60Z\n" + "2012-12-31T23:59:60Z\n" + "2013-12-31T23:59:60Z\n" + "2014-12-31T23:59:60Z\n" + "2015-12-31T23:59:60Z\n" + "2017-12-31T23:59:60Z\n" + "2018-12-31T23:59:60Z\n" + "2019-12-31T23:59:60Z\n" + "2020-12-31T23:59:60Z\n" + "2021-12-31T23:59:60Z\n" + "2022-12-31T23:59:60Z\n" + "2023-12-31T23:59:60Z\n" + "// REJECT: assumes no future leap seconds\n" + "2024-12-31T23:59:60Z\n" + "2099-12-31T23:59:60Z\n" + "9999-12-31T23:59:60Z\n" + "// REJECT: leap seconds only in UTC format\n" + "2005-12-31T23:59:60+00:00\n" + "2008-12-31T23:59:60+00:00\n" + "// REJECT: Not a leap day, year is not a multiple of four\n" + "0101-02-29T04:05:06.007Z\n" + "0102-02-29T04:05:06.007Z\n" + "0103-02-29T04:05:06.007Z\n" + "1537-02-29T04:05:06.007Z\n" + "1538-02-29T04:05:06.007Z\n" + "2001-02-29T04:05:06.007Z\n" + "2002-02-29T04:05:06.007Z\n" + "2003-02-29T04:05:06.007Z\n" + "2021-02-29T04:05:06.007Z\n" + "2022-02-29T04:05:06.007Z\n" + "2023-02-29T04:05:06.007Z\n" + "2025-02-29T04:05:06.007Z\n" + "2026-02-29T04:05:06.007Z\n" + "2027-02-29T04:05:06.007Z\n" + "2029-02-29T04:05:06.007Z\n" + "2030-02-29T04:05:06.007Z\n" + "2031-02-29T04:05:06.007Z\n" + "2033-02-29T04:05:06.007Z\n" + "2034-02-29T04:05:06.007Z\n" + "2035-02-29T04:05:06.007Z\n" + "2037-02-29T04:05:06.007Z\n" + "2038-02-29T04:05:06.007Z\n" + "2039-02-29T04:05:06.007Z\n" + "2041-02-29T04:05:06.007Z\n" + "2042-02-29T04:05:06.007Z\n" + "2043-02-29T04:05:06.007Z\n" + "9997-02-29T04:05:06.007Z\n" + "9998-02-29T04:05:06.007Z\n" + "9999-02-29T04:05:06.007Z\n" + "// REJECT: Not a leap day, year is a multiple of 100 but not 400\n" + "0100-02-29T04:05:06.007Z\n" + "0200-02-29T04:05:06.007Z\n" + "0300-02-29T04:05:06.007Z\n" + "0500-02-29T04:05:06.007Z\n" + "0600-02-29T04:05:06.007Z\n" + "0700-02-29T04:05:06.007Z\n" + "0900-02-29T04:05:06.007Z\n" + "1000-02-29T04:05:06.007Z\n" + "1100-02-29T04:05:06.007Z\n" + "1500-02-29T04:05:06.007Z\n" + "2100-02-29T04:05:06.007Z\n" + "2200-02-29T04:05:06.007Z\n" + "2300-02-29T04:05:06.007Z\n" + "2500-02-29T04:05:06.007Z\n" + "2600-02-29T04:05:06.007Z\n" + "2700-02-29T04:05:06.007Z\n" + "2900-02-29T04:05:06.007Z\n" + "3000-02-29T04:05:06.007Z\n" + "3100-02-29T04:05:06.007Z\n" + "3300-02-29T04:05:06.007Z\n" + "3400-02-29T04:05:06.007Z\n" + "3500-02-29T04:05:06.007Z\n" + "3700-02-29T04:05:06.007Z\n" + "```\n\n" + "```\n" + "(?=\n" + " (?:^\n" + " (?: # All non-leap-second YYYY-MM-DD parts:\n" + " (?:\\d\\d\\d\\d-(?:0[1-9] |10|11|12)-(?:0[1-9]|1[0-9]|2[0-8])) # Days 01-28\n" + " | (?:\\d\\d\\d\\d-(?:0[13-9] |10|11|12)-(29|30)) # Days 29+30\n" + " | (?:\\d\\d\\d\\d-(?:0[13578]|10 |12)-31) # Day 31\n" + " | (?:\\d\\d[2468][048]|\\d\\d0[48]|\\d\\d[13579][26])-02-29 # leap years not divisible by 100\n" + " | (?:[02468][048]00|[13579][26]00)-02-29 # leap years divisible by 400\n" + " )\n" + " T\n" + " (?:(?:0[0-9]|1[0-9]|2[0-3]):(?:[0-5][0-9]):(?:[0-5][0-9])) # time part\n" + " (?:\\.\\d\\d\\d)? # ms part (optional)\n" + " (?:Z|[\\+\\-](?:0[0-9]|1[012]):00|\\+0[34569]:30|\\+10:30|-0[39]:30|\\+1[34]:00|\\+0[58]:45|\\+12:45)\n" + " $)\n" + " |^(?:1972 |198[1235]|199[2347]|2012|2015 )-06-30T23:59:60Z$ # all june leapsecs\n" + " |^(?:197[2-9]|1987|1989|199[058] |2005|2008|2016)-12-31T23:59:60Z$ # all december leapsecs\n" + ")\n" + "(?!.*-00:00$) # if given a -00:00 offset reject unconditionally, psychhhh\n" + "# OK! Since only valid times are now possible, we can use a loose pattern match to parse.\n" + "^(\\d\\d\\d\\d)-(\\d\\d)-(\\d\\d)T(\\d\\d):(\\d\\d):(\\d\\d)(?:\\.(\\d\\d\\d))?((Z)|([\\+\\-])(\\d\\d):(\\d\\d))$\n" + "```"; final Pattern pattern = Pattern.compile(regex, Pattern.MULTILINE); final Matcher matcher = pattern.matcher(string); while (matcher.find()) { System.out.println("Full match: " + matcher.group(0)); for (int i = 1; i <= matcher.groupCount(); i++) { System.out.println("Group " + i + ": " + matcher.group(i)); } } } }

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 Java, please visit: https://docs.oracle.com/javase/7/docs/api/java/util/regex/Pattern.html