Version-specific features
Earthly makes use of feature flags to release new and experimental features. Some features must be explicitly enabled to use them.
Earthly uses semantic versioning; once a new feature has reached stability, a new major or minor version of Earthly will be released with the feature enabled by default.

Specifying Version and features

Each Earthfile should list the current earthly version it depends on using the VERSION command. The VERSION command was first introduced under 0.5 and is optional as of 0.6; however, it will become mandatory in a future version.
VERSION [<flags>...] <version-number>


To Future-proof Earthfiles it is recommended to add a VERSION command. Consider a case where an Earthfile is developed against earthly v0.5.23 and makes use of the experimental FOOBAR command, the first line of the Earthfile should be:
VERSION --foobar 0.5
This will ensure that backwards-breaking features that are introduced in a later version will not change how this Earthfile is interpreted.
In a future release (e.g. 0.X), the FOOBAR command might be promoted from the experimental stage to stable stage, at that point, version 0.X would automatically set the --foobar flag to true, and the Earthfile could be updated to require version 0.X (or later), and could be rewritten as VERSION 0.X.

Feature flags

Feature flag
Speeds up COPY transfers
Changes the behavior of SAVE commands in a significant way
Enables support for FOR ... IN ... commands
Requires --force for saving artifacts locally outside the Earthfile's directory
Eliminates implicit .earthlyignore entries, such as Earthfile and .tmp-earthly-out
Allows shelling-out in any earthly command (including in the middle of ARG)
Note that the features flags are disabled by default in Earthly versions lower than the version listed in the "status" column above.
Speeds up COPY transfers.
When enabled, Earthly will only send the files listed for the specific COPY command. Without this feature, Earthly sends the entire directory of files excluding files listed in the .earthlyignore file.
Changes the behavior of SAVE commands in a significant way
When enabled, Earthly will output artifacts resulting from SAVE ARTIFACT ... AS LOCAL ... and images resulting from SAVE IMAGE and also execute RUN --push commands only if they are connected to the main target through a chain of BUILD commands.
For example, chains like these will produce outputs (and possibly push, if enabled):
  • main target -> SAVE
  • main target -> BUILD -> SAVE
  • main target -> BUILD -> BUILD -> SAVE
  • main target -> BUILD -> BUILD -> BUILD -> SAVE
While chains like these will NOT produce outputs nor would they push:
  • main target -> FROM -> SAVE
  • main target -> COPY -> SAVE
  • main target -> FROM -> BUILD -> SAVE
  • main target -> BUILD -> FROM -> SAVE
  • main target -> BUILD -> BUILD -> COPY -> SAVE
This works the same regardless of whether the targets in the chain are remote or local.
When this feature is disabled, Earthly will output artifacts and images regardless of whether they are connected to the main target through a chain of BUILD commands, however the outputs will be subject to the following rules:
  • All SAVE ARTIFACT ... AS LOCAL ..., with local Earthfiles will be output
  • SAVE ARTIFACT ... AS LOCAL ... produced in remote targets will not be output
  • All images with tag names (both local and remote Earthfiles) will be output
  • No image will be pushed or RUN --push command will be executed if the target is remote
Enables support for FOR ... IN ... commands
When enabled, Earthly will allow the use of FOR ... IN ... commands.