semver

name	semver
description	Enforces Semantic Versioning 2.0.0 (semver.org) rules. Use when choosing a version bump type for a release, validating version strings, tagging releases, handling pre-release or build metadata, managing deprecations, or advising on version precedence.

Semantic Versioning 2.0.0

Reference: https://semver.org/spec/v2.0.0.html

Version Format

MAJOR.MINOR.PATCH[-pre-release][+build]

Segment	When to increment	Reset rule
MAJOR (X)	Backward-incompatible API change	Resets MINOR and PATCH to 0
MINOR (Y)	New backward-compatible functionality or deprecation notice	Resets PATCH to 0
PATCH (Z)	Backward-compatible bug fix only	—

Normative Rules

1. A public API MUST be declared (in code or documentation).
2. Version MUST be X.Y.Z — non-negative integers, no leading zeroes, each MUST increase numerically.
3. Once a version is released, its contents MUST NOT be modified. Any change MUST be a new version.
4. 0.y.z is for initial development — anything MAY change, public API SHOULD NOT be considered stable.
5. 1.0.0 defines the first stable public API.
6. PATCH MUST be incremented for backward-compatible bug fixes only.
7. MINOR MUST be incremented when new backward-compatible functionality is introduced or any public API is deprecated. MAY include patch-level changes.
8. MAJOR MUST be incremented for any backward-incompatible change. MAY include minor and patch-level changes.
9. A released version MUST NOT be altered — even to fix a bug. Release a new version instead.

Pre-release Versions

• Append a hyphen and dot-separated identifiers: 1.0.0-alpha, 1.0.0-alpha.1, 1.0.0-0.3.7
• Identifiers MUST use only [0-9A-Za-z-], MUST NOT be empty, numeric identifiers MUST NOT have leading zeroes.
• Pre-release has lower precedence than the associated normal version: 1.0.0-alpha < 1.0.0

Build Metadata

• Append a + and dot-separated identifiers: 1.0.0+20130313, 1.0.0-beta+exp.sha.5114f85
• Build metadata MUST be ignored when determining precedence.

Precedence

Compare identifiers left to right: MAJOR → MINOR → PATCH → pre-release (build metadata ignored).

Pre-release precedence example:

1.0.0-alpha < 1.0.0-alpha.1 < 1.0.0-alpha.beta < 1.0.0-beta < 1.0.0-beta.2 < 1.0.0-beta.11 < 1.0.0-rc.1 < 1.0.0

Pre-release identifier comparison rules:

• Numeric-only identifiers are compared numerically.
• Alphanumeric identifiers are compared lexically in ASCII order.
• Numeric identifiers have lower precedence than alphanumeric identifiers.
• A larger set of pre-release fields has higher precedence when all preceding identifiers are equal.

Deprecation Workflow

1. Issue a new MINOR release that marks functionality as deprecated (with documentation update).
2. Remove the functionality in a subsequent MAJOR release.
3. Never remove deprecated functionality without a prior minor release that contains the deprecation notice.

Common Pitfalls

Pitfall	Correct behaviour
v1.2.3 is not a SemVer string	The SemVer string is 1.2.3; the v prefix is a tag naming convention, not part of the spec
Modifying a released version	MUST NOT be done — release a new version
Leading zeroes (01.2.3, 1.02.3)	MUST NOT appear in any numeric identifier
Bumping MAJOR for every deprecation	Deprecations warrant a MINOR bump; removal warrants a MAJOR bump
Skipping the deprecation MINOR release	At least one MINOR release with the deprecation MUST precede removal

Initial Development Guidance

• Start at 0.1.0 and increment MINOR for each subsequent release.
• Increment PATCH for backward-compatible bug fixes within the 0.y.z range.
• Promote to 1.0.0 when the software is used in production or has a stable API that users depend on.

Validation Regex

Named groups (PCRE / Python / Go):

^(?P<major>0|[1-9]\d*)\.(?P<minor>0|[1-9]\d*)\.(?P<patch>0|[1-9]\d*)(?:-(?P<prerelease>(?:0|[1-9]\d*|\d*[a-zA-Z-][0-9a-zA-Z-]*)(?:\.(?:0|[1-9]\d*|\d*[a-zA-Z-][0-9a-zA-Z-]*))*))?(?:\+(?P<buildmetadata>[0-9a-zA-Z-]+(?:\.[0-9a-zA-Z-]+)*))?$

Numbered groups (ECMAScript / JavaScript):

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

Checklist

When releasing a new version, verify:

• The change type is correctly identified (bug fix → PATCH, new feature/deprecation → MINOR, breaking change → MAJOR)
• Version string contains no leading zeroes
• Previously released version contents have not been modified
• If deprecating, a MINOR release is made before any future MAJOR removal
• Git tag uses the vX.Y.Z convention (e.g. git tag v1.2.3) while the SemVer string itself is 1.2.3
• CHANGELOG or release notes document the nature of the change