Dockerfile ADD: copying files and remote URLs

ADD copies new files, directories, or remote file URLs from <src> into the image at <dest>.

It can copy from the build context or from remote URLs. If a local archive is added, Docker automatically extracts it. Because ADD has a wide range of behavior, prefer COPY for local files and directories, or use RUN with curl/wget for remote resources (so you can process and clean up downloads in the same layer).