Inside a dependency block, we can declare a library dependency using one of several dependency configurations. The following table shows the differences between them.

configuration	behavior	advantage
implementation	exist in compile time classpath and build output but only visible to other modules at runtime	significantly reduce build time
api	just like implementation, but transtively export to other modules	if using too much, it will sigificantly increase build time
compileOnly	only exists in compile time	reduce the final apk size by not adding transient dependencies that aren’t critical
runtimeOnly	only exists in runtime, in build output
annotationProcessor	if the dependency is an annotation processor