Yii version numbering ===================== Releases -------- A.B.C A = For Yii2 it's always 2. B = Major version. Non-BC changes with upgrade instructions. C = BC changes and additions. Release candidates ------------------ A.B.C-rc A.B.C-rc2 This is when we want to do a release candidate. RC number increments till we're getting a stable release with no critical bugs and backwards incompatibility reports. Alphas and betas ---------------- A.B.C-alpha A.B.C-alpha2 Alphas are unstable versions where significant bugs may and probably do exist. API isn't fixed yet and may be changed significantly. `alpha2` etc. may or may not be released based on overall stability of code and API. A.B.C-beta A.B.C-beta2 Beta is more or less stable with less bugs and API instability than alphas. There still could be changes in API but there should be a significant reason for it.