Regex for Numbers Only

Read it left to right. Each piece below matches one part of the input:

• ^ Start of the string.
• \d+ One or more digits. In JavaScript, \d is exactly [0-9].
• $ End of the string, so nothing else may follow.

The whole input must match, from the first character to the last. Every row below is checked against the pattern by our automated test suite before each release.

Pick the variant that matches what you accept:

• Digits only: ^\d+$ matches 42 and 007.
• Integers with an optional sign: ^[+-]?\d+$ matches -5 and +12.
• Decimals: ^[+-]?(?:\d+\.?\d*|\.\d+)$ matches 3.14, .5 and 10..
• No leading zeros: ^(?:0|[1-9]\d*)$ matches 0 and 120 but not 007.
• Thousands separators: ^\d{1,3}(?:,\d{3})*$ matches 1,234,567.
• Scientific notation: ^[+-]?(?:\d+\.?\d*|\.\d+)(?:[eE][+-]?\d+)?$ matches 6.02e23.

Separators and decimal marks depend on the locale: 1.234,5 in Germany is 1,234.5 in the US. For user input, parse with Intl.NumberFormat-aware code or a library rather than adding every convention to the regex.

It depends on the engine, and the difference causes real bugs:

• JavaScript and Go: \d is [0-9], even with the u flag.
• Python 3 (str patterns), .NET and Java with UNICODE_CHARACTER_CLASS: \d matches any Unicode decimal digit, including Arabic-Indic ٣, Devanagari ३ and full-width ３.

So ^\d+$ in Python accepts "١٢٣", and then int("١٢٣") returns 123, which may or may not be what you want. Use [0-9] (or the re.ASCII flag) when you mean ASCII digits, and \p{Nd} with the u flag in JavaScript when you genuinely want every script.

For an HTML form, inputmode="numeric" shows a number pad without the quirks of type="number" (which accepts e, + and -).

The pattern is translated for each engine rather than pasted as is: named groups, anchors, escapes, shorthand classes and flags are adjusted so each snippet behaves as closely to the JavaScript version as its engine allows. Differences that remain (Go's RE2 has no lookarounds or backreferences, for example) are called out under each one. The Code tab in the tester above also exports Dart, and updates as you edit the pattern.

JavaScript and TypeScript

const regex = /^\d+$/;

function isValid(value) {
  return regex.test(value);
}

console.log(isValid("0"));

Python

import re

pattern = re.compile(r"^[0-9]+\Z")

def is_valid(value: str) -> bool:
    return pattern.search(value) is not None

print(is_valid("0"))

• \d and \w are written as [0-9] and [A-Za-z0-9_] because in Python they also match digits and letters from other scripts.
• JavaScript's $ only matches at the very end of the string. Python's $ also matches before a trailing newline, so the pattern uses \Z instead.

Go

package main

import (
	"fmt"
	"regexp"
)

func main() {
	re := regexp.MustCompile(`^\d+$`)
	fmt.Println(re.MatchString("0"))
}

C#

using System;
using System.Text.RegularExpressions;

// The timeout stops a pathological input from hanging the thread (ReDoS).
var regex = new Regex(@"^[0-9]+\z", RegexOptions.None, TimeSpan.FromSeconds(1));
Console.WriteLine(regex.IsMatch("0"));

• \d and \w are written as [0-9] and [A-Za-z0-9_] because in .NET they also match digits and letters from other scripts.
• JavaScript's $ only matches at the very end of the string. .NET's $ also matches before a trailing newline, so the pattern uses \z instead.

PHP

<?php

$pattern = '/^\d+$/D';

function isValid(string $value, string $pattern): bool
{
    return preg_match($pattern, $value) === 1;
}

var_dump(isValid('0', $pattern));

• The D modifier makes $ match only at the very end, like JavaScript (PCRE's $ also matches before a trailing newline).

• Regex for Alphanumeric Characters: Letters A–Z and digits only, with a Unicode variant for every script.
• Regex for Phone Numbers (E.164 Format): International numbers in E.164: a plus, a country code and up to 15 digits in total.
• Regex for Credit Card Numbers: Visa, Mastercard, Amex, Discover, Diners and JCB by prefix and length (digits only).
• Regex for US ZIP Codes: Five-digit ZIP codes with an optional ZIP+4 extension, like 90210-1234.

Browse all 25 patterns in the regex pattern library, or build your own in the regex tester.