Android Asset Packaging Tool 2.0 (AAPT2) release notes

Version 2.3

Duplicate resource filtering: removes duplicate resources in dominated configurations that are always identical when selected at runtime. This can be disabled with --no-resource-deduping.

Configuration Split APK support: supports splitting resources that match a set of configurations to a separate APK which can be loaded alongside the base APK on API 21+ devices. This is done using the flag --split path/to/split.apk:<config1>[,<config2>,...].
SDK version resource filtering: Resources with an SDK version qualifier that is unreachable at runtime due to the minimum SDK level declared by the AndroidManifest.xml are stripped.

Pseudo-localization: generates pseudolocalized versions of default strings when the --pseudo-localize option is specified.
Legacy mode: treats some class of errors as warnings in order to be more compatible with AAPT when --legacy is specified.
Compile directory: treats the input file as a directory when --dir is specified. This will emit a zip of compiled files, one for each file in the directory. The directory must follow the Android resource directory structure (res/values-[qualifiers]/file.ext).

Automatic attribute versioning: adds version qualifiers to resources that use attributes introduced in a later SDK level. This can be disabled with --no-auto-version.
Min SDK resource filtering: removes resources that can't possibly be selected at runtime due to the application's minimum supported SDK level.