24-Hour Time with Seconds (HH:MM:SS) Regex for JavaScript

What this pattern does

This page provides a well-structured, multi-part regular expression for matching 24-hour time with seconds (hh:mm:ss), ported and verified for JavaScript. A rigorously tested regex reduces debugging time and protects your application from edge-case failures. The snippet below is ready to drop into your JavaScript project — whether you're validating in an Express middleware, a Next.js API route, or a client-side form.

Javascript Implementation

// 24-Hour Time with Seconds (HH:MM:SS)
// ReDoS-safe | RegexVault — Localization > Time Formats

const 24hourTimeWithSecondsHhmmssRegex = /^(2[0-3]|[01][0-9]):([0-5][0-9]):([0-5][0-9])$/;

function validate24hourTimeWithSecondsHhmmss(input: string): boolean {
  return 24hourTimeWithSecondsHhmmssRegex.test(input);
}

// Example
console.log(validate24hourTimeWithSecondsHhmmss("00:00:00")); // true

Test Cases

When to use this pattern

This pattern is drawn from the Localization > Time Formats category and carries a ReDoS-safe certification. That matters for JavaScript developers because especially critical in long-running Node.js event loops where a ReDoS vulnerability can block the entire process. RegexVault audits patterns against known backtracking attack vectors, ensuring you have the necessary context before using this regex in a high-stakes production environment.

Common Pitfalls

Technical Notes

Requires zero-padded hours (09, not 9). Does not include fractional seconds. For sub-second precision, see loc-time-03. Note: 23:59:60 would be a leap second — technically valid in UTC but rare.