@tanstack/router-core/src/ssr/ssr-match-id.ts

Modern and scalable routing for React applications

// Inlined match ids must not look like relative URLs to crawlers, and must only
// contain characters that are valid in the HTML input stream. '#' cannot come
// from a decoded pathname or an encoded param, Seroval emits it unescaped, and
// it keeps the HTML one-byte: a single char above U+00FF makes V8 widen the
// whole concatenated HTML string to two bytes per char, which slows SSR.
// The client compares ids in this encoded form, so no decoder is needed.
export function dehydrateSsrMatchId(id: string): string {
  return id.replaceAll('/', '#')
}