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

/
/
i

Test String

Code Generator

Language

Generated Code

// include the latest version of the regex crate in your Cargo.toml extern crate regex; use regex::Regex; fn main() { let regex = Regex::new(r"(?i)^[a-z](?:[-a-z0-9\+\.])*:(?:\/\/(?:(?:%[0-9a-f][0-9a-f]|[-a-z0-9\._~!\$&'\(\)\*\+,;=:\xA0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF]|[\uD800-\uD83E\uD840-\uD87E\uD880-\uD8BE\uD8C0-\uD8FE\uD900-\uD93E\uD940-\uD97E\uD980-\uD9BE\uD9C0-\uD9FE\uDA00-\uDA3E\uDA40-\uDA7E\uDA80-\uDABE\uDAC0-\uDAFE\uDB00-\uDB3E\uDB44-\uDB7E][\uDC00-\uDFFF]|[\uD83F\uD87F\uD8BF\uD8FF\uD93F\uD97F\uD9BF\uD9FF\uDA3F\uDA7F\uDABF\uDAFF\uDB3F\uDB7F][\uDC00-\uDFFD])*@)?(?:\[(?:(?:(?:[0-9a-f]{1,4}:){6}(?:[0-9a-f]{1,4}:[0-9a-f]{1,4}|(?:[0-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5])(?:\.(?:[0-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5])){3})|::(?:[0-9a-f]{1,4}:){5}(?:[0-9a-f]{1,4}:[0-9a-f]{1,4}|(?:[0-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5])(?:\.(?:[0-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5])){3})|(?:[0-9a-f]{1,4})?::(?:[0-9a-f]{1,4}:){4}(?:[0-9a-f]{1,4}:[0-9a-f]{1,4}|(?:[0-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5])(?:\.(?:[0-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5])){3})|(?:[0-9a-f]{1,4}:[0-9a-f]{1,4})?::(?:[0-9a-f]{1,4}:){3}(?:[0-9a-f]{1,4}:[0-9a-f]{1,4}|(?:[0-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5])(?:\.(?:[0-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5])){3})|(?:(?:[0-9a-f]{1,4}:){0,2}[0-9a-f]{1,4})?::(?:[0-9a-f]{1,4}:){2}(?:[0-9a-f]{1,4}:[0-9a-f]{1,4}|(?:[0-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5])(?:\.(?:[0-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5])){3})|(?:(?:[0-9a-f]{1,4}:){0,3}[0-9a-f]{1,4})?::[0-9a-f]{1,4}:(?:[0-9a-f]{1,4}:[0-9a-f]{1,4}|(?:[0-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5])(?:\.(?:[0-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5])){3})|(?:(?:[0-9a-f]{1,4}:){0,4}[0-9a-f]{1,4})?::(?:[0-9a-f]{1,4}:[0-9a-f]{1,4}|(?:[0-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5])(?:\.(?:[0-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5])){3})|(?:(?:[0-9a-f]{1,4}:){0,5}[0-9a-f]{1,4})?::[0-9a-f]{1,4}|(?:(?:[0-9a-f]{1,4}:){0,6}[0-9a-f]{1,4})?::)|v[0-9a-f]+[-a-z0-9\._~!\$&'\(\)\*\+,;=:]+)\]|(?:[0-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5])(?:\.(?:[0-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5])){3}|(?:%[0-9a-f][0-9a-f]|[-a-z0-9\._~!\$&'\(\)\*\+,;=@\xA0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF]|[\uD800-\uD83E\uD840-\uD87E\uD880-\uD8BE\uD8C0-\uD8FE\uD900-\uD93E\uD940-\uD97E\uD980-\uD9BE\uD9C0-\uD9FE\uDA00-\uDA3E\uDA40-\uDA7E\uDA80-\uDABE\uDAC0-\uDAFE\uDB00-\uDB3E\uDB44-\uDB7E][\uDC00-\uDFFF]|[\uD83F\uD87F\uD8BF\uD8FF\uD93F\uD97F\uD9BF\uD9FF\uDA3F\uDA7F\uDABF\uDAFF\uDB3F\uDB7F][\uDC00-\uDFFD])*)(?::[0-9]*)?(?:\/(?:(?:%[0-9a-f][0-9a-f]|[-a-z0-9\._~!\$&'\(\)\*\+,;=:@\xA0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF]|[\uD800-\uD83E\uD840-\uD87E\uD880-\uD8BE\uD8C0-\uD8FE\uD900-\uD93E\uD940-\uD97E\uD980-\uD9BE\uD9C0-\uD9FE\uDA00-\uDA3E\uDA40-\uDA7E\uDA80-\uDABE\uDAC0-\uDAFE\uDB00-\uDB3E\uDB44-\uDB7E][\uDC00-\uDFFF]|[\uD83F\uD87F\uD8BF\uD8FF\uD93F\uD97F\uD9BF\uD9FF\uDA3F\uDA7F\uDABF\uDAFF\uDB3F\uDB7F][\uDC00-\uDFFD]))*)*|\/(?:(?:(?:(?:%[0-9a-f][0-9a-f]|[-a-z0-9\._~!\$&'\(\)\*\+,;=:@\xA0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF]|[\uD800-\uD83E\uD840-\uD87E\uD880-\uD8BE\uD8C0-\uD8FE\uD900-\uD93E\uD940-\uD97E\uD980-\uD9BE\uD9C0-\uD9FE\uDA00-\uDA3E\uDA40-\uDA7E\uDA80-\uDABE\uDAC0-\uDAFE\uDB00-\uDB3E\uDB44-\uDB7E][\uDC00-\uDFFF]|[\uD83F\uD87F\uD8BF\uD8FF\uD93F\uD97F\uD9BF\uD9FF\uDA3F\uDA7F\uDABF\uDAFF\uDB3F\uDB7F][\uDC00-\uDFFD]))+)(?:\/(?:(?:%[0-9a-f][0-9a-f]|[-a-z0-9\._~!\$&'\(\)\*\+,;=:@\xA0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF]|[\uD800-\uD83E\uD840-\uD87E\uD880-\uD8BE\uD8C0-\uD8FE\uD900-\uD93E\uD940-\uD97E\uD980-\uD9BE\uD9C0-\uD9FE\uDA00-\uDA3E\uDA40-\uDA7E\uDA80-\uDABE\uDAC0-\uDAFE\uDB00-\uDB3E\uDB44-\uDB7E][\uDC00-\uDFFF]|[\uD83F\uD87F\uD8BF\uD8FF\uD93F\uD97F\uD9BF\uD9FF\uDA3F\uDA7F\uDABF\uDAFF\uDB3F\uDB7F][\uDC00-\uDFFD]))*)*)?|(?:(?:(?:%[0-9a-f][0-9a-f]|[-a-z0-9\._~!\$&'\(\)\*\+,;=:@\xA0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF]|[\uD800-\uD83E\uD840-\uD87E\uD880-\uD8BE\uD8C0-\uD8FE\uD900-\uD93E\uD940-\uD97E\uD980-\uD9BE\uD9C0-\uD9FE\uDA00-\uDA3E\uDA40-\uDA7E\uDA80-\uDABE\uDAC0-\uDAFE\uDB00-\uDB3E\uDB44-\uDB7E][\uDC00-\uDFFF]|[\uD83F\uD87F\uD8BF\uD8FF\uD93F\uD97F\uD9BF\uD9FF\uDA3F\uDA7F\uDABF\uDAFF\uDB3F\uDB7F][\uDC00-\uDFFD]))+)(?:\/(?:(?:%[0-9a-f][0-9a-f]|[-a-z0-9\._~!\$&'\(\)\*\+,;=:@\xA0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF]|[\uD800-\uD83E\uD840-\uD87E\uD880-\uD8BE\uD8C0-\uD8FE\uD900-\uD93E\uD940-\uD97E\uD980-\uD9BE\uD9C0-\uD9FE\uDA00-\uDA3E\uDA40-\uDA7E\uDA80-\uDABE\uDAC0-\uDAFE\uDB00-\uDB3E\uDB44-\uDB7E][\uDC00-\uDFFF]|[\uD83F\uD87F\uD8BF\uD8FF\uD93F\uD97F\uD9BF\uD9FF\uDA3F\uDA7F\uDABF\uDAFF\uDB3F\uDB7F][\uDC00-\uDFFD]))*)*|(?!(?:%[0-9a-f][0-9a-f]|[-a-z0-9\._~!\$&'\(\)\*\+,;=:@\xA0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF]|[\uD800-\uD83E\uD840-\uD87E\uD880-\uD8BE\uD8C0-\uD8FE\uD900-\uD93E\uD940-\uD97E\uD980-\uD9BE\uD9C0-\uD9FE\uDA00-\uDA3E\uDA40-\uDA7E\uDA80-\uDABE\uDAC0-\uDAFE\uDB00-\uDB3E\uDB44-\uDB7E][\uDC00-\uDFFF]|[\uD83F\uD87F\uD8BF\uD8FF\uD93F\uD97F\uD9BF\uD9FF\uDA3F\uDA7F\uDABF\uDAFF\uDB3F\uDB7F][\uDC00-\uDFFD])))(?:\?(?:%[0-9a-f][0-9a-f]|[-a-z0-9\._~!\$&'\(\)\*\+,;=:@\/\?\xA0-\uD7FF\uE000-\uFDCF\uFDF0-\uFFEF]|[\uD800-\uD83E\uD840-\uD87E\uD880-\uD8BE\uD8C0-\uD8FE\uD900-\uD93E\uD940-\uD97E\uD980-\uD9BE\uD9C0-\uD9FE\uDA00-\uDA3E\uDA40-\uDA7E\uDA80-\uDABE\uDAC0-\uDAFE\uDB00-\uDB3E\uDB44-\uDB7E\uDB80-\uDBBE\uDBC0-\uDBFE][\uDC00-\uDFFF]|[\uD83F\uD87F\uD8BF\uD8FF\uD93F\uD97F\uD9BF\uD9FF\uDA3F\uDA7F\uDABF\uDAFF\uDB3F\uDB7F\uDBBF\uDBFF][\uDC00-\uDFFD])*)?(?:\#(?:%[0-9a-f][0-9a-f]|[-a-z0-9\._~!\$&'\(\)\*\+,;=:@\/\?\xA0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF]|[\uD800-\uD83E\uD840-\uD87E\uD880-\uD8BE\uD8C0-\uD8FE\uD900-\uD93E\uD940-\uD97E\uD980-\uD9BE\uD9C0-\uD9FE\uDA00-\uDA3E\uDA40-\uDA7E\uDA80-\uDABE\uDAC0-\uDAFE\uDB00-\uDB3E\uDB44-\uDB7E][\uDC00-\uDFFF]|[\uD83F\uD87F\uD8BF\uD8FF\uD93F\uD97F\uD9BF\uD9FF\uDA3F\uDA7F\uDABF\uDAFF\uDB3F\uDB7F][\uDC00-\uDFFD])*)?$").unwrap(); let string = "http://foo.com?a=|"; // result will be a tuple containing the start and end indices for the first match in the string let result = regex.captures(string); let (start, end) = match result { Some((s, e)) => (s, e), None => { // ... } }; println!("{}", &string[start, end]); }

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 Rust, please visit: https://docs.rs/regex/latest/regex/