[schwartzworld]

Serverside includes are a thing in Apache or nginx.

If you don’t mind a little coding, it wouldn’t take long to build a tool that lets you store the bodies as template files, wraps them in the header/footer, and minifies them.

Even less effort is pandoc’s standalone mode which lets you provide a wrapper template.

[gibbitz]

Yeah SSI solved this 30 years ago. It's kind of a fire and forget solution too.