.. _faq_deprecation:

How are configuration deprecations handled?

As documented in the "Breaking change policy" in :repo:CONTRIBUTING.md, features can be marked as deprecated at any point as long as there is a replacement available. Each deprecation is annotated in the API proto itself and explained in detail in the :ref:Envoy documentation <deprecated>.

For the first 3 months following deprecation, use of deprecated fields will result in a logged warning and incrementing the :ref:deprecated_feature_use <runtime_stats> counter. After that point, the field will be annotated as fatal-by-default and further use of the field will be treated as invalid configuration unless :ref:runtime overrides <config_runtime_deprecation> are employed to re-enable use.