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 # Breaking changes and incompatibilities
 
 Every Engine release strives to be backward compatible with its predecessors.
 In all cases, the policy is that feature removal is communicated two releases
 in advance and documented as part of the [deprecated features](deprecated.md)
 page.
 
 Unfortunately, Docker is a fast moving project, and newly introduced features
 may sometime introduce breaking changes and/or incompatibilities. This page
 documents these by Engine version.
 
 # Engine 1.10
 
 There were two breaking changes in the 1.10 release.
 
 ## Registry
 
 Registry 2.3 includes improvements to the image manifest that have caused a
 breaking change. Images pushed by Engine 1.10 to a Registry 2.3 cannot be
 pulled by digest by older Engine versions. A `docker pull` that encounters this
 situation returns the following error:
 

 ```
  Error response from daemon: unsupported schema version 2 for tag TAGNAME

 ```
 
 Docker Content Trust heavily relies on pull by digest. As a result, images
 pushed from the Engine 1.10 CLI to a 2.3 Registry cannot be pulled by older
 Engine CLIs (< 1.10) with Docker Content Trust enabled.
 
 If you are using an older Registry version (< 2.3), this problem does not occur
 with any version of the Engine CLI; push, pull, with and without content trust
 work as you would expect.
 
 ## Docker Content Trust
 
 Engine older than the current 1.10 cannot pull images from repositories that

 have enabled key delegation. Key delegation is a feature which requires a
 manual action to enable.