k8s-sidecar-injector vs Weave: What are the differences?

Developers describe k8s-sidecar-injector as "Kubernetes sidecar injection service". It is a small service that runs in each Kubernetes cluster, and listens to the Kubernetes API via webhooks. For each pod creation, the injector gets a (mutating admission) webhook, asking whether or not to allow the pod launch, and if allowed, what changes we would like to make to it. On the other hand, Weave is detailed as "Weave creates a virtual network that connects Docker containers deployed across multiple hosts". Weave can traverse firewalls and operate in partially connected networks. Traffic can be encrypted, allowing hosts to be connected across an untrusted network. With weave you can easily construct applications consisting of multiple containers, running anywhere.

k8s-sidecar-injector and Weave can be categorized as "Container" tools.

k8s-sidecar-injector and Weave are both open source tools. Weave with 5.57K GitHub stars and 517 forks on GitHub appears to be more popular than k8s-sidecar-injector with 143 GitHub stars and 19 GitHub forks.