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

/
/
g

Test String

Code Generator

Language

Generated Code

import java.util.regex.Matcher; import java.util.regex.Pattern; public class Example { public static void main(String[] args) { final String regex = "e[yw][A-Za-z0-9-_]+\\.(?:e[yw][A-Za-z0-9-_]+)?\\.[A-Za-z0-9-_]{2,}(?:(?:\\.[A-Za-z0-9-_]{2,}){2})?"; final String string = "JWT pattern\n\n" + "- handles both JWS (3 segments) and JWE (5 segments)\n" + " - remove the ending `(?:(?:...` to handle JWS only\n" + "- segments 1+2 are expected tp start with `e[yw]`, an encoded start of JSON object `{\"` or `{\\n`\n" + " - remove/extend it to match used token structure\n" + " - or make it even more restrictive `(ey[IJ]|ewo)` to match encoded `{\"\\w` or `{\\n\"`\n" + "- payload (2nd segment) may be empty\n" + "- both header (1st segment) and payload are expected to start with `eyJ`, a base64 encoded start of JSON object `{\"`\n" + "- accepts only proper Base64url encoding (RFC 4648) without Base64 padding `=`\n" + "- test it at https://regex101.com/r/V99DS0\n\n" + "eyJhbGciOiJkaXIiLCJlbmMiOiJBMjU2Q0JDLUhTNTEyIiwia2lkIjoicEw1NGdLalBHWElQVWw3eGlGN3B5MExJY3IxNkhPVlZnTXBtWjZqZmFUcUppb1h6M0FSM21EaWpTdXFxNnNvSTBoM1BaNzdMdDUzRjVUbVVPRW5KRGcifQ..LxFPkpn8Gu8vFuXDtOKA1A.DkMr_qOgv6zdyFiZGnz01wnFfLLmoMpRA-L3EbmgOGv21E-yU8ks7C_MSwA6E8KpXAB7XHeejJQWvs5ZrxDM2G8_t_BIJ6DUFXvLvLOzdo0hceeCCtujAgMPsjxW0RQFHkrA2VOlpuF7vVgJXPby19t0_QBWIaZnpfnAYzDJ98UpO1WbNxqGfdpbNG6RETpH.w1H3V7eGynuOi2qJUooceTCvoC4P5sT7bQRqbLZuyR0"; final Pattern pattern = Pattern.compile(regex); final Matcher matcher = pattern.matcher(string); while (matcher.find()) { System.out.println("Full match: " + matcher.group(0)); for (int i = 1; i <= matcher.groupCount(); i++) { System.out.println("Group " + i + ": " + matcher.group(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 Java, please visit: https://docs.oracle.com/javase/7/docs/api/java/util/regex/Pattern.html