How does compose behavior with already pulled or started docker images

Hi all,

we uses docker-compose to fire up our dev environnements , we push or a regular basis updates of our Docker images into our registry.

i’ve been wondering what really makes compose to pull updates from the registry ?
our devs launch docker-compose up -d every morning, but updates aren’t pulled on a regular basis, we haven’t found how this really works :frowning:

can anyone please enlighten me ?