Two URLs like /foo and /foo/ might look the same, but they’re actually different. A relative URL like ./bar will resolve to /bar in the first case and /foo/bar in the second, and search engines will treat them as separate entries, harming your SEO.

In short, being loosey-goosey about trailing slashes is a bad idea. By default, SvelteKit strips trailing slashes, meaning that a request for /foo/ will result in a redirect to /foo.

If you instead want to ensure that a trailing slash is always present, you can specify the trailingSlash option accordingly:

export const trailingSlash = 'always';

To accommodate both cases (this is not recommended!), use 'ignore':

export const trailingSlash = 'ignore';

The default value is 'never'.

Whether or not trailing slashes are applied affects prerendering. A URL like /always/ will be saved to disk as always/index.html whereas a URL like /never will be saved as never.html.