Starting with Bolt 2, the versioning scheme will be inspired from Semantic Versioning and Unity’s (undocumented) versioning scheme. That is:

Given a version number MAJOR.MINOR.PATCHpPREVIEW, increment the:

1. MAJOR version when you make incompatible changes to the serialization format, package structure, or API
2. MINOR version when you add functionality in a backwards-compatible manner
3. PATCH version when you make backwards-compatible bug fixes
4. PREVIEW when you make changes to preview releases

p, the PREVIEW RELEASE PREFIX, can be either:

• a for ALPHA, a feature-incomplete preview release
• b for BETA, a feature-complete preview
• x-LABEL. for EXPERIMENTAL, a feature-branch preview release

Increment the PREVIEW version when a release:

• for ALPHA, adds functionality in a backwards-compatible manner
• for BETA, makes backwards-compatible bug fixes
• for EXPERIMENTAL, makes any kind of change

ALPHA and BETA releases should be only be used for MAJOR.MINOR.0 versions, given that PATCH versions should only contain bug fixes to the stable final version.

EXPERIMENTAL version numbers should specify their LABEL, with a dash after the PREVIEW RELEASE PREFIX and a period before the RELEASE.

For EXPERIMENTAL versions, MAJOR.MINOR.PATCH indicates the release from which the feature-preview is branched.