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

/
/
gmx

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 = "^\n" + "(?P<group>\n" + " (?P<structured>\n" + " (?P<single>\n" + " (?P<tag_first>\n" + " (?P<tag>\n" + " \\d+(?:\\/\\d+)+\n" + " |\n" + " (?P<repnum>\\$+(?:@\\^*-?\\d*)?)\n" + " |\n" + " [\\w:!-]\n" + " )++\n" + " (?P<attr>\n" + " (?P<short_attr>\n" + " \\.\n" + " (?P<short_val>\n" + " (?P>repnum)\n" + " |\n" + " [\\w:!-]\n" + " )*\n" + " |\n" + " \\#(?P>short_val)*\n" + " )\n" + " |\n" + " (?P<long_attr>\n" + " \\[\n" + " (?P<attr_pair>\n" + " (?P<attr_name>\n" + " \\\\(?:\\\\{2})*[\"'\\s]\n" + " |\n" + " [^\\[\\]\"'\\s\\\\]\n" + " )+\n" + " \\.?\n" + " (?P<equal_val>\n" + " =\n" + " (?P<attr_val>\n" + " (?P<unquoted_val>\n" + " \\\\(?:\\\\{2})*[\\[\\]\"'\\s]\n" + " |\n" + " [^\\[\\]\"'\\s\\\\]\n" + " )+\n" + " |\n" + " (?P<quoted_val>\n" + " (?P<quote>[\"'])\n" + " (?:\n" + " (?P<escaped_all>\\\\(?:\\\\{2})*.)\n" + " |\n" + " [^\"'\\n\\\\]\n" + " )*\n" + " (?P=quote)\n" + " )\n" + " )?\n" + " )?\n" + " )?\n" + " (?:\\s+(?P>attr_pair))*\n" + " \\]\n" + " )\n" + " )*\n" + " |\n" + " (?P>attr)+\n" + " )\n" + " (?P<tag_rest>\n" + " (?P<text>\n" + " \\{\n" + " (?P<text_content>\n" + " (?P>escaped_all)\n" + " |\n" + " [^\\{\\}\\n\\\\]\n" + " )*\n" + " \\}\n" + " )\n" + " (?P>attr)*\n" + " (?:\n" + " (?P<rep>\\*\\d*+)?\n" + " (?P>attr)*\n" + " (?P<close>\\/)?\n" + " |\n" + " (?P>close)?\n" + " (?P>rep)?\n" + " )\n" + " |\n" + " (?P>rep)\n" + " (?P>attr)*\n" + " (?P>text)?\n" + " (?P>attr)*\n" + " (?P>close)?\n" + " |\n" + " (?P>close)\n" + " (?P>rep)?\n" + " )?\n" + " |\n" + " (?P<text_first>(?P>text)(?P>attr)*)\n" + " (?P<text_rest>\n" + " (?P>rep)\n" + " (?P>attr)*\n" + " (?P>close)?\n" + " |\n" + " (?P>close)\n" + " (?P>rep)?\n" + " )?\n" + " )\n" + " (?:\n" + " (?P<relation>[>+]|\\^+)\n" + " (?P>group)*\n" + " )?\n" + " )\n" + "|\n" + " \\(\n" + " (?P>group)*\n" + " \\)\n" + " (?P>rep)?\n" + " (?P>relation)?\n" + ")+\n" + "$"; final String string = ">>> tag <<<\n" + "tag\n" + "$\n" + "tag$with$@^^^-2repnum\n" + "1\n" + "1/2\n" + "1/2/3\n" + "tag1/2with1/2/3fraction\n" + "tag$@with1/2both\n" + "ri:a\n" + "!\n" + "!!!\n" + "-\n" + ":\n\n" + "===XXX===\n" + "@\n" + "&\n\n" + ">>> short attr <<<\n" + "#\n" + "###\n" + "#id\n" + "#id1#id2\n" + "#id$@^^^-2\n" + ".\n" + ".#\n" + "...\n" + ".class\n" + ".class1.class2\n" + ".class#id.class\n" + ".class$@^-2type\n" + ".class-data\n" + ".!class\n" + ".class:subclass\n\n" + "===XXX===\n" + ".@\n" + ".汉字\n\n" + ">>> long attr <<<\n" + "[]\n" + "[key]\n" + "[key.]\n" + "[key...]\n" + "[key=]\n" + "[key.=]\n" + "[key=val]\n" + "[key.=val]\n" + "[key='val']\n" + "[key='val with space']\n" + "[key='val\\\\\\'ue']\n" + "[key1=val1 key2=val2]\n" + "[][]\n" + "[key][key]\n" + ".class[key]\n" + "[key].class\n" + "[汉字=汉字]\n\n" + "===XXX===\n" + "[\\[]\n" + "[key='val\\\\'ue']\n\n" + ">>> text <<<\n" + "{}\n" + "{text}\n" + "{text with space}\n" + "{text with escaped \\{ and \\}}\n" + "{汉字}\n" + "tag{text}\n" + ".attr{text}\n" + "{text}.attr\n\n" + "===XXX===\n" + "{\\\\{}\n" + "{{}}\n\n" + ">>> repeater <<<\n" + "tag*2\n" + ".attr*2\n" + "{text}*2\n" + ".attr{text}*2\n" + ".attr{text}.attr*2\n\n" + "===XXX===\n" + "*2\n" + "tag*2*2\n\n" + ">>> self-close <<<\n" + "tag/\n" + ".attr/\n" + "{text}/\n" + "tag*2/\n" + "tag/*2\n" + ".attr{text}.attr/\n" + ".attr*2.attr{text}.attr/\n" + ".attr{text}.attr*2.attr/\n" + ".attr{text}/*2\n" + "tag*2{text}/\n\n" + "===XXX===\n" + "/*2\n" + "tag//\n\n" + ">>> child <<<\n" + "tag>tag\n" + "tag.class*2>tag[key]/\n" + "tag>\n\n" + "===XXX===\n" + ">tag\n" + "tag>>\n\n" + ">>> sibling <<<\n" + "tag+tag\n" + ".class/>[key]+.attr/*2\n" + "tag[key]tag\n" + "tag{text}tag\n" + "tag*2tag\n" + "tag/tag\n\n" + "===XXX===\n" + "+tag\n" + "tag++\n\n" + ">>> parent <<<\n" + "tag^tag\n" + "tag^^^\n" + "tag>tag+tag^tag\n\n" + "===XXX===\n" + "^tag\n\n" + ">>> group <<<\n" + "()\n" + "(())\n" + "(tag)\n" + "(tag)(tag)\n" + "((tag)(tag))\n" + "tag>(tag.class)\n" + "tag>(tag>tag+tag)\n" + "(tag>(tag+tag)*2)*2\n" + "(tag)tag\n" + "(tag>).class\n" + "(tag)*2^tag\n" + "(tag*2)^tag\n" + "(tag>)^tag\n" + "(tag)^\n\n" + "===XXX===\n" + "(\n" + "(()"; final Pattern pattern = Pattern.compile(regex, Pattern.MULTILINE | Pattern.COMMENTS); 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