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

Code Generator

Language

Generated Code

const regex = /^hsla?\(\s*(?<h>[-+]?\d{1,3}(?:\.\d+)?)(deg|grad|rad|turn)?\s*(?:,\s*|\s+)\s*(?<s>[-+]?\d{1,3}(?:\.\d+)?)%\s*(?:,\s*|\s+)\s*(?<l>[-+]?\d{1,3}(?:\.\d+)?)%\s*(?:,\s*|\s+)?(?:\s*\/?\s*(?<alpha>[-+]?[\d.]+%?)\s*)?\)$/gmi; // Alternative syntax using RegExp constructor // const regex = new RegExp('^hsla?\\(\\s*(?<h>[-+]?\\d{1,3}(?:\\.\\d+)?)(deg|grad|rad|turn)?\\s*(?:,\\s*|\\s+)\\s*(?<s>[-+]?\\d{1,3}(?:\\.\\d+)?)%\\s*(?:,\\s*|\\s+)\\s*(?<l>[-+]?\\d{1,3}(?:\\.\\d+)?)%\\s*(?:,\\s*|\\s+)?(?:\\s*\\\/?\\s*(?<alpha>[-+]?[\\d.]+%?)\\s*)?\\)$', 'gmi') const str = ` hsl(.9, .99%, .999%, .9999) hsl(0240, 0100%, 0050%, 01) hsl(2400, 1000%, 1000%, 10) hsl(-2400.01deg, -1000.5%, -1000.05%, -100) hsl(2.40e+2, 1.00e+2%, 5.00e+1%, 1E-3) hsl(-240, -100%, -50%, -0.1) hsl(+240, +100%, +50%, +0.1) HSL(240Deg, 100%, 50%) hsl(240, 100%, 50%, 10%) hsl(150deg 30% 60%) hsl(0.3turn 60% 45% .7) hsl(0.3grad 60% 45% / .7) hsl(0.3rad 60% 45% / .7) hsl(12 60% 45% / .7) hsl(120, 100%, 50%) hsl(0, 0%, 0%) hsl(60, 50%, 75%) hsl(270, 80%, 60%) hsl(200, 20%, 40%) hsl(340, 90%, 80%) hsla(120, 100%, 50%, 0.5) hsla(0, 0%, 0%, 0.2) hsla(60, 50%, 75%, 0.8) hsla(270, 80%, 60%, 0.4) hsla(200, 20%, 40%, 0.6) hsla(340, 90%, 80%, 0.1) hsl(120 100% 50%) hsl(0 0% 0%) hsl(60 50% 75%) hsl(270 80% 60%) hsl(200 20% 40%) hsl(340 90% 80%) hsla(120 100% 50% / 0.5) hsla(0 0% 0% / 0.2) hsla(60 50% 75% / 0.8) hsla(270 80% 60% / 0.4) hsla(200 20% 40% / 0.6) hsla(340 90% 80% / 0.1) hsl(240, 100%, 50%) hsl(240, 100%, 50%, 0.1) hsl(240,100%,50%,0.1) hsl(180deg, 100%, 50%, 0.1) hsl(3.14rad, 100%, 50%, 0.1) hsl(200grad, 100%, 50%, 0.1) hsl(0.5turn, 100%, 50%, 0.1) hsl(240.5, 99.99%, 49.999%, 0.9999) hsl(240.0, 100.00%, 50.000%, 1.0000) hsl(240 100% 50%) hsl(240 100% 50% / 0.1) hsla(240, 100%, 50%) hsla(240, 100%, 50%, 0.1) `; // Reset `lastIndex` if this regex is defined globally // regex.lastIndex = 0; let m; while ((m = regex.exec(str)) !== null) { // This is necessary to avoid infinite loops with zero-width matches if (m.index === regex.lastIndex) { regex.lastIndex++; } // The result can be accessed through the `m`-variable. m.forEach((match, groupIndex) => { console.log(`Found match, group ${groupIndex}: ${match}`); }); }

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