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

r"
"
g

Test String

Code Generator

Generated Code

package main import ( "regexp" "fmt" ) func main() { var re = regexp.MustCompile(`(?:(?<=^)|(?<=\s))(?:(?:https?|ftp)://)?((?:[^\W_]|-)[^\W_]*(?:-[^\W_]*)*(?:\.(?:[^\W_]|-)[^\W_]*(?:-[^\W_]*)*)*\.[^\W_][^\W_]*)(?::\d+)?/(?:[\w~_.:/?#\[\]@!$&'*+,;=()-]*(?:(?:%[0-9a-fA-F][0-9a-fA-F])+[\w~_.:/?#\[\]@!$&'*+,;=()-]*)*)?(?=\s|$)`) var str = `IP Address: 93.114.205.169 0.0.0.0 0.0.0.0 10.10.10.10 99.99.99.99 199.199.199.199 255.255.255.255 256.256.256.256 02.02.02.02 111.222.13.255 1.2.3.4 1.2.3.4.5 11.22.33.44 11.22.33.44.55 255.0.1.254 255.0.1.254 In a text 255.0.1.254 there is an IP address In a text 10.10.10.10 there is an IP address In a text 93.114.205.169 there is an IP address Domain: example.com https://sub5-7.example.com/ https://sub5-7.example.com sub.sub2.example.com www.example.com https://sub.example.com http://example.com ftp://sub.mit-example222.com In a text www.example.com there is an domain. In a text https://sub5-7.example.com there is an domain. In a text www.example.com there is an domain. URL 93.114.205.169:443/path 93.114.205.169/path example.com/path sub.example.com/path 93.114.205.169/path https://sub5-7.example.com/ http://example.com/ example.com/ sub.example.com:443/ www.--example.com/ www.examp--le.com/ www.example.co/ www.example.c/ example.com/path ftp://sub.mit-example222.com:8080// ftp://sub.mit-example222.com/%12 sub.example.com/path sub.example.com/path sub.example.com:80/path sub.example.com/path/path/path/p/a/q/1$%h sub.example.com/path/path/path/p/a/q/1$%1f sub.example.com/path/path/%aa%1f%3dpath/p/a/q/1$%1f111 https://sub.example.com/path/path http://sub.example.com/path/path http://something.com/#$SLJFHsdq32908432098=!~abc In a text example.com/path there is an URL path. In a text www.example.com/path there is an URL path. In a text www.blog.example.com/path there is an URL path. In a text sub.example.com/paththere is an URL path. In a text sub.example.com/path/path/path/p/a/q/1$%h there is an URL path. In a text sub.example.com/path/path/path/p/a/q/ there is an URL path. ` for i, match := range re.FindAllString(str, -1) { fmt.Println(match, "found at index", 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 Golang, please visit: https://golang.org/pkg/regexp/