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"
"
gm

Test String

Code Generator

Language

Generated Code

package main import ( "regexp" "fmt" ) func main() { var re = regexp.MustCompile(`(?m)^((?:https?://(?:www\.)?|www\.)(?:(?!-)[A-Za-z0-9-]+\.[a-z]+)(?:\/[A-Za-z0-9-_]+\/?)*(?:[?&][A-Za-z0-9-\=\+_]+)*(?:\.[a-z]+)*)$|^((?:\d{1,3}\.){3}\d{1,3}(?:\:\d+)?)$`) var str = `http://www.google.com http://google.com https://www.google.com https://google.com www.abcdefghijklmnopqrstuvwxyz123456789-.com http://www.abcdefghijklmnopqrstuvwxyz123456789-.com https://www.crummy.com/software/wow/ https://www.crummy.com/software?wow=1 https://www.crummy.com/software/examples/hello?wow=1&yep=ok https://www.crummy.com/software?wow=1+and+2&yep=ok https://www.crummy.com/software/BeautifulSoup/bs4/doc/_sources/index.txt Outliers http://www.google http://wwww.google.com http://ww.google.com https://w.g.c 255.255.255.255:5555 192.168.9.50:22 127.0.0.1 127.0.0.1:8080 www.google google.com google ww.google.c ht://www.google.com www.-google.com ` 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/