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

/
/
gmi

Test String

Substitution

Processing...

Code Generator

Language

Generated Code

const regex = /(^## assemble\/assemble-boilerplate-markdown starts)([\s\S]*?)(^## assemble\/assemble-boilerplate-markdown ends)/gmi; // Alternative syntax using RegExp constructor // const regex = new RegExp('(^## assemble\\\/assemble-boilerplate-markdown starts)([\\s\\S]*?)(^## assemble\\\/assemble-boilerplate-markdown ends)', 'gmi') const str = `## assemble/assemble-boilerplate-markdown starts ## assemble/assemble-boilerplate-markdown ends ## assemble/assemble-boilerplate-markdown starts /assemble-boilerplate-markdown/src/content/TOC /assemble-boilerplate-markdown/src/content/markdown/auto-links /assemble-boilerplate-markdown/src/content/markdown/autolink-lines /assemble-boilerplate-markdown/src/content/markdown/backslash-escapes /assemble-boilerplate-markdown/src/content/markdown/blockquote-list-item /assemble-boilerplate-markdown/src/content/markdown/blockquotes-with-code-blocks /assemble-boilerplate-markdown/src/content/markdown/case-insensitive-refs /assemble-boilerplate-markdown/src/content/markdown/code-blocks /assemble-boilerplate-markdown/src/content/markdown/code-spans /assemble-boilerplate-markdown/src/content/markdown/def-blocks /assemble-boilerplate-markdown/src/content/markdown/double-link /assemble-boilerplate-markdown/src/content/markdown/escaped-angles /assemble-boilerplate-markdown/src/content/markdown/gfm-break /assemble-boilerplate-markdown/src/content/markdown/gfm-code-hr-list /assemble-boilerplate-markdown/src/content/markdown/gfm-code /assemble-boilerplate-markdown/src/content/markdown/gfm-del /assemble-boilerplate-markdown/src/content/markdown/gfm-em /assemble-boilerplate-markdown/src/content/markdown/gfm-links /assemble-boilerplate-markdown/src/content/markdown/gfm-tables /assemble-boilerplate-markdown/src/content/markdown/hard-wrapped-paragraphs-with-list-like-lines /assemble-boilerplate-markdown/src/content/markdown/horizontal-rules /assemble-boilerplate-markdown/src/content/markdown/hr-list-break /assemble-boilerplate-markdown/src/content/markdown/inline-html-advanced /assemble-boilerplate-markdown/src/content/markdown/inline-html-comments /assemble-boilerplate-markdown/src/content/markdown/inline-html-simple /assemble-boilerplate-markdown/src/content/markdown/lazy-blockquotes /assemble-boilerplate-markdown/src/content/markdown/links-inline-style /assemble-boilerplate-markdown/src/content/markdown/links-reference-style /assemble-boilerplate-markdown/src/content/markdown/links-shortcut-references /assemble-boilerplate-markdown/src/content/markdown/list-item-text /assemble-boilerplate-markdown/src/content/markdown/literal-quotes-in-titles /assemble-boilerplate-markdown/src/content/markdown/loose-lists /assemble-boilerplate-markdown/src/content/markdown/main /assemble-boilerplate-markdown/src/content/markdown/markdown-documentation-basics /assemble-boilerplate-markdown/src/content/markdown/markdown-documentation-syntax /assemble-boilerplate-markdown/src/content/markdown/nested-blockquotes /assemble-boilerplate-markdown/src/content/markdown/nested-code /assemble-boilerplate-markdown/src/content/markdown/nested-em /assemble-boilerplate-markdown/src/content/markdown/nested-square-link /assemble-boilerplate-markdown/src/content/markdown/not-a-link /assemble-boilerplate-markdown/src/content/markdown/ordered-and-unordered-lists /assemble-boilerplate-markdown/src/content/markdown/same-bullet /assemble-boilerplate-markdown/src/content/markdown/strong-and-em-together /assemble-boilerplate-markdown/src/content/wiki/data-context /assemble-boilerplate-markdown/src/content/wiki/data-types /assemble-boilerplate-markdown/src/content/wiki/data-yaml-front-matter /assemble-boilerplate-markdown/src/content/wiki/data-yaml /assemble-boilerplate-markdown/src/content/wiki/data /assemble-boilerplate-markdown/src/content/wiki/options-assets /assemble-boilerplate-markdown/src/content/wiki/options-collections /assemble-boilerplate-markdown/src/content/wiki/options-data /assemble-boilerplate-markdown/src/content/wiki/options-engine /assemble-boilerplate-markdown/src/content/wiki/options-ext /assemble-boilerplate-markdown/src/content/wiki/options-helpers /assemble-boilerplate-markdown/src/content/wiki/options-layout /assemble-boilerplate-markdown/src/content/wiki/options-layoutdir /assemble-boilerplate-markdown/src/content/wiki/options-partials /assemble-boilerplate-markdown/src/content/wiki/options /assemble-boilerplate-markdown/src/content/wiki/templates-helpers /assemble-boilerplate-markdown/src/content/wiki/templates-layouts /assemble-boilerplate-markdown/src/content/wiki/templates-partials ## assemble/assemble-boilerplate-markdown ends`; const subst = `xxx`; // The substituted value will be contained in the result variable const result = str.replace(regex, subst); console.log('Substitution result: ', result);

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