--- title: "Both trailing-slash and non-slash URLs serve 200 (seo/trailing-slash)" description: "seo/trailing-slash: /about and /about/ are different URLs; serving both creates duplicates that split links and crawl budget." canonical: https://void-design.vercel.app/rules/seo/trailing-slash lastModified: 2026-09-16 --- # Both trailing-slash and non-slash URLs serve 200 `seo/trailing-slash` · severity **error** · category SEO · detected by `void seo` and `void audit` ## Why it matters /about and /about/ are different URLs; serving both creates duplicates that split links and crawl budget. ## How to fix it Pick one form (Next.js default: no slash, via 308) and make the other permanently redirect. Keep canonicals, sitemap and links on the same form. ## Example ```ts // next.config.ts — default is trailingSlash: false (/about/ → 308 → /about) const nextConfig: NextConfig = { trailingSlash: false } ``` ## References - https://nextjs.org/docs/app/api-reference/config/next-config-js/trailingSlash - https://developers.google.com/search/docs/crawling-indexing/consolidate-duplicate-urls ## More seo rules `void seo` reports 60 rules in this category. What search engines need from the raw response: status codes, titles and descriptions in , self-referencing canonicals, one h1, crawlable links, Open Graph, icons, robots.txt and a sitemap with real dates. - `img-alt-quality` Alt text is a filename, a generic word, or overly long — [seo/img-alt-quality](https://void-design.vercel.app/rules/seo/img-alt-quality) - `links-not-crawlable` Navigation uses elements crawlers can't follow — [seo/links-not-crawlable](https://void-design.vercel.app/rules/seo/links-not-crawlable) - `link-text` Links with generic or empty text — [seo/link-text](https://void-design.vercel.app/rules/seo/link-text) - `broken-links` Internal links return 4xx/5xx (or go through redirects) — [seo/broken-links](https://void-design.vercel.app/rules/seo/broken-links) - `hreflang-invalid` hreflang uses invalid codes or relative URLs — [seo/hreflang-invalid](https://void-design.vercel.app/rules/seo/hreflang-invalid) - `hreflang-not-reciprocal` hreflang set isn't self-referencing and reciprocal — [seo/hreflang-not-reciprocal](https://void-design.vercel.app/rules/seo/hreflang-not-reciprocal) - `og-missing` Required Open Graph tags missing (og:title, og:type, og:image, og:url) — [seo/og-missing](https://void-design.vercel.app/rules/seo/og-missing) - `og-incomplete` og:description / og:site_name missing, or og:url ≠ canonical — [seo/og-incomplete](https://void-design.vercel.app/rules/seo/og-incomplete) Detected by `void seo` and `void audit`. Explain it in a terminal: `void rules seo/trailing-slash`