How to remove .html from the post URL?

When I try to change the URL with fornt-matter form url: "/example.html" to url: "/example" . The page will run without the style and static files. But if the URL includes .html it will be run fine… why is that?
How can I remove .html from post URLs?

It seems that you have enabled uglyURLs in your project’s config. You need to remove it.

No, there is no such a thing in my config

No need to post the same reply again.

I have no idea what you’re doing and what you’re trying to do.

Also see the Requesting Help topic, some useful tips in there.

I use this structure for my content/posts:

If I remove the .html from the URL the result won’t load the static files.
I can provide the link to the code repo too. because it’s public.

I noticed if I add {{ .Site.BaseURL }} before my /css in my head.html partial, it will load the style.
now the URL is <link rel="stylesheet" href=" {{ .Site.BaseURL }}/css/main.css" />
should {{ .Site.BaseURL }} be always included in header?
But post images still won’t run.