Regex for Semantic Version (SemVer) — Pattern Explained with Examples

Semantic Versioning (SemVer) is a versioning scheme used by most modern software packages. This pattern validates the MAJOR.MINOR.PATCH format with optional pre-release labels and build metadata according to the SemVer 2.0.0 specification.

The Pattern

/^(0|[1-9]\d*)\.(0|[1-9]\d*)\.(0|[1-9]\d*)(-[a-zA-Z0-9.-]+)?(\+[a-zA-Z0-9.-]+)?$/

Pattern Breakdown

Matches

• 1.0.0
• 2.1.3
• 0.0.1
• 1.0.0-alpha
• 2.0.0+build.2024
• 1.2.3-beta.1+build99

Does NOT Match

• 1.0
• 1.0.0.0
• v1.0.0
• 01.0.0
• 1.0.0-alpha. (trailing dot)
• 1.0.0-alpha..beta

Language Examples

JavaScript

const semverRegex = /^(0|[1-9]\d*)\.(0|[1-9]\d*)\.(0|[1-9]\d*)(-[a-zA-Z0-9.-]+)?(\+[a-zA-Z0-9.-]+)?$/;
console.log(semverRegex.test('1.0.0'));         // true
console.log(semverRegex.test('01.0.0'));        // false
console.log(semverRegex.test('1.0.0-alpha.1')); // true

Python

import re
pattern = r'^(0|[1-9]\d*)\.(0|[1-9]\d*)\.(0|[1-9]\d*)(-[a-zA-Z0-9.-]+)?(\+[a-zA-Z0-9.-]+)?$'
print(bool(re.match(pattern, '1.0.0')))           # True
print(bool(re.match(pattern, '01.0.0')))          # False
print(bool(re.match(pattern, '1.0.0-beta+exp')))  # True

Common Pitfalls

• Leading zeros are prohibited in SemVer — 01.0.0 is invalid because 01 is parsed as 1 but the spec forbids leading zeros for unambiguous sorting
• Pre-release precedence is lower than the release version (1.0.0-alpha < 1.0.0), but build metadata is ignored for precedence — this pattern validates syntax only
• The v prefix (e.g., v1.0.0) is common in git tags but is not part of the SemVer spec — strip the prefix before validation or add v? at the start
• Pre-release and build metadata identifiers are dot-separated; consecutive dots (1.0.0-alpha..1) are invalid
• Each pre-release or build identifier must be alphanumeric or hyphen — identifiers with spaces or special characters are rejected

Real-World Use Cases

• npm package validation — ensure package.json version fields conform to SemVer before publishing
• CI/CD pipeline checks — validate version tags in git before building and deploying releases
• API version negotiation — parse and compare API version strings in HTTP headers for routing requests

FAQ

Related Patterns

Regex for Numbers Regex for Date (YYYY-MM-DD)