docker-compose : Unsupported config option for services service: 'web'

Since this is the first result on Googling "docker-compose Unsupported config option for services", I would like to add that the most common reason as of 2020 is missing of version: "3".

Just add version: "3" to the start of your docker-compose.yml.

From the docs:

There are currently three versions of the Compose file format:

1. Version 1, the legacy format. This is specified by omitting a version key at the root of the YAML.
2. Version 2.x. This is specified with a version: '2' or version: '2.1', etc., entry at the root of the YAML.
3. Version 3.x, the latest and recommended version, designed to be cross-compatible between Compose and the Docker Engine’s swarm mode. This is specified with a version: '3' or version: '3.1', etc., entry at the root of the YAML.

Support for the version 2 compose file format was introduced in docker-compose version 1.6, released around February of this year.

You're using 1.3.3, from July 2015.

You need to upgrade to a more recent version to use the version 2 format configuration files.