How to create 404 error page in fragmenium

Create a plain HTML file named 404.html in the site’s root directory. Populate it with all required markup that conforms to the default structure. Within the body, clearly explain why the visitor was redirected to this page and provide fallback paths that guide them back to functional sections of the site.

The Fragmanium engine intercepts client-side navigation and redirects the visitor to this 404 page whenever a requested route does not exist. Because Fragmanium runs entirely in the browser, it cannot influence the initial HTTP request; the redirection happens only after a valid page has loaded and Fragmanium is active.

Static hosts (e.g., Cloudflare Pages, Netlify, GitHub Pages) will automatically serve /404.html for any unmatched path, ensuring the custom error page is still reached on a hard reload or direct link. Developers who control their own server must configure it to return the same 404.html file for invalid paths.