Is Gradle not offline by default?

I am very new to Gradle (coming from maven), our organization uses an artifactory to hold dependencies and also has a bunch of custom plugins.

When I tried to execute a gradle build without connecting to our org’s VPN, I got an error which suggests that Gradle is trying to reach out to the interet

A problem occurred configuring project ':PROJECT_NAME'.
> Could not resolve all artifacts for configuration ':PROJECT_NAME:classpath'
        > Could not HEAD 'custom.artifactory.url/artifactory/repo2/org/codehaus/groovy/groovy/maven-metadata.xml'.
               > No such host is known (

When I added --offline then I was able to build to project.

So, my question is:

Is gradle not offline by default? Or, is it some issue with our org’s custom plugins that’s not allowing Gradle to used cached versions?

I’d guess you either have a dynamic version (like 1+ or a version range), or a changing version (like a SNAPSHOT version).
For these Gradle regularly has to check whether resolution result is different now.
To prevent that and use the last result, you exactly have the --offline switch.