What is an example of a matching and non-matching string?

A valid matching string is "@devtransform". A non-matching string is "@this_username_is_way_too_long_for_x".

Is this regex safe from ReDoS (Catastrophic Backtracking)?

Yes, this pattern is optimized for linear execution time and safe for browser-side validation without locking up the UI thread.

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Twitter / X Username Handle Regex

Q: How do I test this regex in JavaScript and TypeScript?

Use regex.test(): const regex = /^@?[a-zA-Z0-9_]{1,15}$/; const isValid = regex.test(inputString);

Validates Twitter and X user handles, allowing an optional leading @ symbol and up to 15 alphanumeric or underscore characters.

Regular Expression Pattern:

/^@?[a-zA-Z0-9_]{1,15}$/

Valid Match Example:

@devtransform

Invalid / Non-Match Example:

@this_username_is_way_too_long_for_x

Regex Syntax Breakdown & Explanation

•^@? : Optional leading @ symbol
•[a-zA-Z0-9_]{1,15}$ : Restricts handle length to Twitter policy max of 15 chars

Implementation in Popular Languages

JavaScript / TypeScript

const regex = /^@?[a-zA-Z0-9_]{1,15}$/;
const isValid = regex.test("@devtransform");
console.log(isValid); // true

Python (re)

import re

pattern = r"^@?[a-zA-Z0-9_]{1,15}$"
match = re.match(pattern, "@devtransform")
print(bool(match)) # True

Go (regexp)

package main
import (
  "fmt"
  "regexp"
)

func main() {
  re := regexp.MustCompile(`^@?[a-zA-Z0-9_]{1,15}$`)
  fmt.Println(re.MatchString("@devtransform"))
}

Frequently Asked Questions

Everything you need to know regarding specifications, syntax, and security best practices.

The regular expression pattern is /^@?[a-zA-Z0-9_]{1,15}$/. Validates Twitter and X user handles, allowing an optional leading @ symbol and up to 15 alphanumeric or underscore characters.