The Varnish Configuration Language (VCL) is a small domain-specific language designed to be used to define request handling within Varnish. It is extremely flexible and allows you to let Varnish do exactly whatever you want or need it to do.

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VCL, which stands for Varnish Configuration Language, is used to define your own caching policies in Varnish Cache and Varnish Enterprise. It is a real programming language whose syntax can in some cases be the same as the C language.