Compose file version 3 reference
These topics describe version 3 of the Compose file format. This is the newest version. There are several versions of the Compose file format - 1, 2, 2.x, and 3.x. The table below is a quick look. For full details on what each version includes and how to upgrade, see About versions and upgrading .
https://docs.docker.com/compose/compose-file/compose-file-v3/#environment