Regular Expressions 101

Save & Manage Regex

  • Current Version: 3
  • Save & Share
  • Community Library

Flavor

  • PCRE2 (PHP)
  • ECMAScript (JavaScript)
  • Python
  • Golang
  • Java
  • .NET 7.0 (C#)
  • Rust
  • PCRE (Legacy)
  • Regex Flavor Guide

Function

  • Match
  • Substitution
  • List
  • Unit Tests
Sponsors
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
Processing...

Test String

Code Generator

Language

Generated Code

import re regex = re.compile(r"(^127\.0\.0\.1[\s]+|^0\.0\.0\.0[\s]+)([0-9a-z_.-]+$)|^([0-9a-z_.-]+$)", flags=re.MULTILINE | re.IGNORECASE) test_str = ("# hpHosts - FSA only\n" "#\n" "# The following are hosts in the hpHosts database with the FSA classification ONLY.\n" "#\n" "127.0.0.1 localhost #IPv4 localhost\n" "127.0.0.1 localhost\n" "::1 localhost #IPv6 localhost\n" "#\n" "# BAD SITES START HERE\n" "#\n" "0.0.0.0 very#badexample.com\n" "very#badexample.com\n" "domain@with.com\n" "doma$in\n" "AuThedMine.cOm\n" "domain.0cf\n" "127.0.0.1 0-0-----------------------------------------------------------0.com\n" "127.0.0.1 0-google.com\n" "127.0.0.1 00-lawyer.com\n" "127.0.0.1 0000.support\n" "0.01.2.13.3.sydneypropertyinvestors.com\n" "0.01.2.23.3.sydneypropertyinvestors.com\n" "000.9.009.09.ekurbani.com\n" "000.9.019.09.ekurbani.com\n" "000000-0.000webhostapp.com\n" "00004563.000webhostapp.com\n" "000m8ih.wcomhost.com\n" "000m8n1.wcomhost.com\n" "000m8pk.wcomhost.com\n" "000m9w3.wcomhost.com\n" "000macu.wcomhost.com\n" "000magu.wcomhost.com\n" "000map9.wcomhost.com\n" "000may2.wcomhost.com\n" "000mhl7.wcomhost.com\n" "000mhpe.wcomhost.com\n" "000mhpg.wcomhost.com\n" "1xbet86.com\n" "1xbet87.com\n" "1xbet90.com\n" "1xbet31.com\n" "1xbet46.com\n" "1xbet28.com\n" "1xbet35.com\n" "1xbet49.com\n" "nejakyhost.cz\n" "0.0.0.0 cnhv.co\n" "0.0.0.0 coin-hive.com\n" "0.0.0.0 coinhive.com\n" "0.0.0.0 authedmine.com\n" "0.0.0.0 api.jsecoin.com\n" "0.0.0.0 load.jsecoin.com\n" "0.0.0.0 server.jsecoin.com\n" "0.0.0.0 miner.pr0gramm.com\n" "0.0.0.0 minemytraffic.com\n" "0.0.0.0 crypto-loot.com\n" "0.0.0.0 cryptaloot.pro\n" "0.0.0.0 cryptoloot.pro\n" "0.0.0.0 coinerra.com\n" "0.0.0.0 coin-have.com\n" "0.0.0.0 minero.pw\n" "0.0.0.0 minero-proxy-01.now.sh\n" "0.0.0.0 minero-proxy-02.now.sh\n" "0.0.0.0 minero-proxy-03.now.sh\n" "0.0.0.0 api.inwemo.c\n" "127.0.0.1 sfdfsdfsdfsdfsd\n" "pool.pebblemedia.adhese.com") matches = regex.finditer(test_str) for match_num, match in enumerate(matches, start=1): print(f"Match {match_num} was found at {match.start()}-{match.end()}: {match.group()}") for group_num, group in enumerate(match.groups(), start=1): print(f"Group {group_num} found at {match.start(group_num)}-{match.end(group_num)}: {group}")

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 Python, please visit: https://docs.python.org/3/library/re.html