Positive Integer Validation Regex

Validate positive integers (zero and positive whole numbers) using a simple regex pattern.

Pattern Breakdown

^\d+$

Components

Character Classes

• \d - Any digit (0-9)
• + - Quantifier: one or more occurrences

Examples

Valid:

• 0
• 1
• 123
• 999999
• 1000000

Invalid:

• -5 (negative number)
• 12.5 (decimal)
• +5 (plus sign)
• 123 (leading space)
• 123 (trailing space)
• abc (non-numeric)

Implementation

JavaScript

const positiveIntRegex = /^\d+$/;
positiveIntRegex.test('123'); // true
positiveIntRegex.test('0'); // true
positiveIntRegex.test('-5'); // false (negative)
positiveIntRegex.test('12.5'); // false (decimal)
positiveIntRegex.test('abc'); // false (non-numeric)

Python

import re
positive_int_regex = r'^\d+$'
bool(re.match(positive_int_regex, '123'))  # True
bool(re.match(positive_int_regex, '0'))  # True
bool(re.match(positive_int_regex, '-5'))  # False (negative)
bool(re.match(positive_int_regex, '12.5'))  # False (decimal)

Go

positiveIntRegex := regexp.MustCompile(`^\d+$`)
positiveIntRegex.MatchString("123") // true
positiveIntRegex.MatchString("0") // true
positiveIntRegex.MatchString("-5") // false (negative)
positiveIntRegex.MatchString("12.5") // false (decimal)

Limitations

1. Includes zero: Matches 0 (use ^[1-9]\d*$ if zero should be excluded)
2. No leading zeros: Accepts 0123 (may want to prevent this)
3. No size limit: Doesn't enforce maximum value
4. String validation: Validates string format, not actual integer type
5. No scientific notation: Doesn't support 1e5 format

When to Use

• Positive integer input validation
• Count/quantity inputs
• ID validation (if IDs are numeric)
• When you need simple positive number validation
• Form input validation

For production, consider:

• Excluding zero if needed: ^[1-9]\d*$
• Preventing leading zeros: ^(0|[1-9]\d*)$
• Adding maximum value validation
• Converting to integer type after validation
• Handling edge cases for very large numbers