Ensuring smooth upgrades of your projects is our first priority. That's why

we promise you backwards compatibility (BC) for all minor Symfony releases.

You probably recognize this strategy as `Semantic Versioning`_. In short,

Semantic Versioning means that only major releases (such as 2.0, 3.0 etc.) are

allowed to break backwards compatibility. Minor releases (such as 2.5, 2.6 etc.)