[DJHenk]

My guess: no-one needs it.

Originally, iframe were the solution, like the posts mentions. By the time iframes became unfashionable, nobody was writing HTML with their bare hands anymore. Since then, people use a myriad of other tools and, as also mentioned, they all have a way to fix this.

So the only group who would benefit from a better iframe is the group of people who don't use any tools and write their HTML with their bare hands in 2025. That is an astonishing small group. Even if you use a script to convert markdown files to blog posts, you already fall outside of it.

No-one needs it, so the iframe does not get reinvented.

[Svip]

No, originally frameset[0] and frame[1] were the solution to this problem. I remember building a website in the late 1990s with frameset. iframe came later, and basically allowed you to do frames without the frameset. Anyway, frameset is also the reason every browser's user agent starts with "Mozilla".

[0] https://developer.mozilla.org/en-US/docs/Web/HTML/Reference/...

[1] https://developer.mozilla.org/en-US/docs/Web/HTML/Reference/...

[chgs]

Originally my footers and navbars were included with server side includes

[micromacrofoot]

what if it could be a larger group though? modern css has been advancing rather rapidly... I don't even need a preprocessing library any more... I've got nested rules, variables, even some light data handling... why not start beefing up html too? we've got some new features but includes would be killer