HTTP 404 Not Found

HTTP 404 Not Found — The server can't find anything at the requested URL.

Class

4xx Client Error

Defined in

RFC 9110 §15.5.5

Official

Yes (IANA registry)

Cacheable by default

Yes (heuristically, per RFC 9110)

Safe to retry

Not without changing the request

What does HTTP 404 mean?

404 Not Found means the server has no resource at the requested URL — or isn't willing to say that one exists. It says nothing about whether the absence is temporary or permanent (use 410 Gone for deliberate, permanent removal).

It's the most famous HTTP error and, for websites, a normal part of life: deleted pages, typos and broken links all produce it. What matters is serving a helpful 404 page and fixing links you control.

When is 404 used?

• A page or file was deleted or moved without a redirect.
• A typo in a link or the address bar.
• An API route or resource id doesn't exist (GET /api/users/99999).
• A single-page app is deployed without a fallback, so refreshing /dashboard 404s on the server.

Common causes of a 404

• Broken internal or external links pointing at old URLs.
• Case-sensitive paths on Linux servers (/About vs /about).
• Missing build output or wrong root/try_files configuration in nginx.
• A routing rule or rewrite that doesn't match after a deploy.

How to fix 404 Not Found

If you're visiting the site

1. Check the URL for typos and wrong capitalisation.
2. Go up one level in the path, or use the site's search or navigation.
3. Search for the page title on a search engine, or check the Wayback Machine (web.archive.org) for removed pages.

If you run the site or API (developers)

1. Add 301 redirects for moved content, and fix internal links (crawl your site to find them).
2. Make sure missing pages return a real 404 status, not a 200 "soft 404".
3. For SPAs, configure a fallback to index.html (nginx try_files $uri /index.html;) and render a 404 view client-side for unknown routes.
4. Monitor 404s in your logs or Search Console's Pages report and redirect the ones with traffic or backlinks.

Returning or handling 404: server examples

server {
    root /var/www/site;
    error_page 404 /404.html;
    location / {
        try_files $uri $uri/ =404;   # SPA: try_files $uri /index.html;
    }
}

app.get("/api/users/:id", async (req, res) => {
  const user = await db.users.find(req.params.id);
  if (!user) return res.status(404).json({ error: "not_found" });
  res.json(user);
});

// Catch-all after every route
app.use((req, res) => res.status(404).send("Page not found"));

// app/blog/[slug]/page.tsx
import { notFound } from "next/navigation";

export default async function Post({ params }) {
  const post = await getPost((await params).slug);
  if (!post) notFound(); // renders app/not-found.tsx with status 404
  return <article>{post.title}</article>;
}

Example 404 response

HTTP/1.1 404 Not Found
Content-Type: text/html; charset=utf-8
Cache-Control: no-cache
Content-Length: 1532

Do 404 errors hurt SEO?

404s for pages that genuinely don't exist are normal and don't hurt your site's rankings; Google simply drops those URLs over time. Problems arise when important pages 404 by mistake, when many internal links are broken (wasting crawl budget and frustrating users), or when a moved page with backlinks 404s instead of redirecting — its link equity is lost. Fix those with 301 redirects.

Related status codes

• 410 GoneThe resource used to exist but was removed on purpose and won't come back.
• 403 ForbiddenThe server understood the request but refuses to authorize it.
• 301 Moved PermanentlyThe resource has a new permanent URL, given in the Location header.

Related tools

• HTTP status codes — full list
• HTTP headers reference
• cURL converter
• Mock API — fake REST endpoints with custom status codes
• Webhook tester — inspect incoming requests