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

A valid matching string is "f47ac10b-58cc-4372-a567-0e02b2c3d479". A non-matching string is "invalid-uuid-string".

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.

HomeRegex LibraryUUID v4 Identifier Validation Regex

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UUID v4 Identifier Validation Regex

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

Use regex.test(): const regex = /^[0-9a-f]{8}-[0-9a-f]{4}-4[0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$/i; const isValid = regex.test(inputString);

Validates 36-character canonical random UUID version 4 format.

Regular Expression Pattern:

/^[0-9a-f]{8}-[0-9a-f]{4}-4[0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$/i

Valid Match Example:

f47ac10b-58cc-4372-a567-0e02b2c3d479

Invalid / Non-Match Example:

invalid-uuid-string

Regex Syntax Breakdown & Explanation

•^[0-9a-f]{8} : 8 hex digits
•-[0-9a-f]{4} : 4 hex digits
•-4[0-9a-f]{3} : Version 4 prefix with 3 hex digits
•-[89ab][0-9a-f]{3} : Variant bits (8, 9, a, or b)
•-[0-9a-f]{12}$ : 12 hex digits node identifier

Implementation in Popular Languages

JavaScript / TypeScript

const regex = /^[0-9a-f]{8}-[0-9a-f]{4}-4[0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$/i;
const isValid = regex.test("f47ac10b-58cc-4372-a567-0e02b2c3d479");
console.log(isValid); // true

Python (re)

import re

pattern = r"^[0-9a-f]{8}-[0-9a-f]{4}-4[0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$"
match = re.match(pattern, "f47ac10b-58cc-4372-a567-0e02b2c3d479")
print(bool(match)) # True

Go (regexp)

package main
import (
  "fmt"
  "regexp"
)

func main() {
  re := regexp.MustCompile(`^[0-9a-f]{8}-[0-9a-f]{4}-4[0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$`)
  fmt.Println(re.MatchString("f47ac10b-58cc-4372-a567-0e02b2c3d479"))
}

Frequently Asked Questions

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

The regular expression pattern is /^[0-9a-f]{8}-[0-9a-f]{4}-4[0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$/i. Validates 36-character canonical random UUID version 4 format.