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

/
/
igum

Test String

Code Generator

Language

Generated Code

package main import ( "regexp" "fmt" ) func main() { var re = regexp.MustCompile(`(?im)([-\.\w]+:\/{2,3})(?!.*[.]{2})(?![-.*\.])((?!.*@\.)[-_\w@^=%&:;~+\.]+(?<![-\.]))(\/[-_\w@^=%&:;/~+\.]+(?<!\.))?\??([-_\w=&@$!|~+]+)*#?([-_\w=&@$!|~+]+)*`) var str = `DB_URL=postgresql://postgres:postgres@localhost/postgres?timeout=0 # Damn, Daniel! Bob: have you checked https://www.facebook.com? lorem https://github.com/justsml?tab=activity#top ipsum smb:///winbox/dfs/ - ipp://printer leading text chrome-extension://flags??# s3://buckets/for/all?true=true s3:///////buckets-o-fun pkcs11://because-pkcs7-is-weak#only=hash \||@@https://www.google.com <- should match when extracting https://we - this is valid s3://buckets-o-fun/!hi/raw=val&#keep=hashin'? http://aaa.com.co.com:8080/test?dan=dev#den hi. pkcs11://because-pkcs7-is-weak hi. a://b/c?d=e#f=g && a://b/c?d] hi. chrome-extension://flags hi. hi. ms-help://good-luck/index.html hi. hi. .iris.beep://really/dots. hi. hi. iris.beep://really/dots?test=qs hi. --- a://b]/c - Should match \`a://b\` - it's smallest match. http://www.c:ool.com.au - this one's tricky, should match auth URIs: proto://user:pass@host. Including cases where the password could be omitted (\`proto://user@host\`.) boop://really-/ -- technically domains shouldn't end in dashes or other 'special' chars, but this is technically a valid URI. --- a://b./c?d. -- bad dns, trailing dot: tricky w/o look-arounds. (Adding an OR pattern would muddle the returned data indexes.) -- should match \`a://b\` Invalid Examples: https://www...google...com https://we@.com https://asdas-.com http://-apple-.com a://(b/c chrome-extension)://flags ms-help://|good-luck.html . , ; : ) ] } ` 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/