Regular Expressions 101

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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 = "\\b(127\\.(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\.(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\.(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)|0?10\\.(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\.(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\.(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)|172\\.0?1[6-9]\\.(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\.(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)|172\\.0?2[0-9]\\.(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\.(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)|172\\.0?3[01]\\.(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\.(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)|192\\.168\\.(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\.(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)|169\\.254\\.(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\.(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)|::1|[fF][cCdD][0-9a-fA-F]{2}(?:[:][0-9a-fA-F]{0,4}){0,7}|[fF][eE][89aAbB][0-9a-fA-F](?:[:][0-9a-fA-F]{0,4}){0,7})(?:\\/([789]|1?[0-9]{2}))?\\b"; final String string = "# loopback\n" + "127.0.0.0\n" + "127.0.0.0000 # only three digits supported here\n\n" + "# A\n" + "10.0.0.1/10\n" + "10.255.22.33\n\n" + "# B\n" + "172.17.100.155/32\n\n" + "# C\n" + "192.168.1.1\n" + "192.168.1.255\n\n" + "# IPv6\n" + "fc00:833e:d648:f196:5c6c:1d9a:a14b:0d59\n" + "fc01:67e5::6a66:34a7\n" + "FC02:5fcf:e093:bb10:ce77:b5c9::/112\n" + "fc03:49bd:b7c1:5685:fa0a:87e9::2/128\n" + "fc04:::2 hmpf\n" + "# Public IP addresses\n" + "0de9:b022:883f:2c3c:7dba:a184:7576:4531\n" + "04e4:e53b:0c2f:2990:27ad:0464:6dd3:b6b3\n" + "0319:3b4a:546e:d480:4814:f885:3396:bba2\n" + "5394:03f5:606f:273e:e343:d94a:610a:3f2e\n" + "63cd:ad1f:7ffb:62c7:cc17:6e20:9b59:2f7d\n\n" + "# More \"crap\"\n" + "30.168.1.255.1\n" + "127.1\n" + "192.168.1.256\n" + "-1.2.3.4\n" + "1.1.1.1.\n" + "3...3\n" + "255.255.255.255\n" + "0.0.0.0\n" + "1.1.1.01\n" + "192.99.16.30\n\n" + "# decimal vs. octal mix\n" + "172.032.33.33\n" + "172.033.33.33\n\n" + "# octal - not supported here\n" + "0254.0021.0062.0041\n\n" + "# link-local addresses IPv4\n" + "169.254.1.0\n" + "169.254.254.255\n\n" + "# link-local addresses IPv6\n" + "fe90:1234::/64\n" + "feaf:ffff::/128\n" + "febf:ffff:ffff:ffff:ffff:ffff:ffff:ffff\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