Experimental Features ===================== All Symfony features benefit from our :doc:`Backward Compatibility Promise ` to give developers the confidence to upgrade to new versions safely and more often. But sometimes, a new feature is controversial or you cannot find a convincing API. In such cases, we prefer to gather feedback from real-world usage, adapt the API, or remove it altogether. Doing so is not possible with a no BC-break approach. To avoid being bound to our backward compatibility promise, such features can be marked as **experimental** and their classes and methods must be marked with the ``@experimental`` tag. A feature can be marked as being experimental for only one minor version, and can never be introduced in an :ref:`LTS version `. The core team can decide to extend the experimental period for another minor version on a case by case basis. To ease upgrading projects using experimental features, the changelog must explain backward incompatible changes and explain how to upgrade code.