HTTP status codes for site audits: 3xx, 4xx and 5xx
An HTTP status code is the three-digit code a server sends with every response. How Google treats 3xx, 4xx and 5xx, and the checks squirrelscan runs.
An HTTP status code is the three-digit number a server sends at the start of every response: 2xx for success, 3xx for a redirect (or, with 304, a cached copy that is still valid), 4xx for a client error and 5xx for a server error.
Google documents how its crawlers treat each class. A 200 goes on to indexing, though indexing is not guaranteed. Redirects are followed up to 10 hops. All 4xx codes except 429 mean the content does not exist: the URL is not indexed, an indexed one is removed, and any body is ignored. A 5xx or a 429 makes the crawlers slow down. Already indexed URLs stay for a while but are eventually dropped if the errors continue.
Category: Links
Why it matters
The status code is what a crawler believes, whatever the page says. An error page sent with 200 is a soft 404: it gets crawled and can be indexed as thin content, and Search Console reports it as a soft 404. A 404 for a removed page is the right answer, and Google calls it a strong signal not to crawl the URL again. A script or stylesheet that answers 404 after a deploy leaves a page that returns 200 but renders broken.
How squirrelscan checks it
links/broken-links compares every internal link with the status the crawl recorded and fails targets that answered 400 or above. Rate-limited and refused targets are reported as unverifiable instead, and targets the audit never fetched are not counted as broken. crawl/sitemap-4xx lists sitemap entries that answer 4xx. crawl/soft-404 detects error content served with 200 and re-fetches the page to confirm. reliability/broken-resources checks the status of every script, stylesheet and font the pages reference, and fails first-party scripts and stylesheets that answer 4xx or 5xx. Throttled and challenged responses are reported as unverified, and a capped or skipped fetch is noted as a partial check. images/broken-images is narrower than its name: it flags an empty, # or data:error image source and sends no request, so a well-formed image URL that answers 404 passes it.
| Rule | What it flags | Severity |
|---|---|---|
| Broken internal links: 404s inside your own site | An internal link to a page that returns 404 or 500 is a dead end you control. squirrel cross-references every internal link against the crawl. | error |
| 4XX pages in sitemap: dead URLs you are still submitting | A sitemap entry that returns 404 wastes a crawl and teaches search engines to trust the file less. squirrel reports the status of every checked entry. | warning |
| Soft 404: error content served with an HTTP 200 status | A not-found page that answers 200 gets crawled and can be indexed as thin content. squirrel detects the error shell and re-checks it before reporting. | warning |
| Broken images: empty and placeholder src attributes | An img with an empty or placeholder src renders as a broken icon. squirrel collects image sources across the crawl and flags the malformed ones. | error |
| Broken scripts, stylesheets and fonts: files that do not load | A page whose script or stylesheet returns 404 or 500 looks fine to a crawler but renders unstyled or never runs its interactive parts. squirrel checks every script, stylesheet and font the crawl fetched. | error |
How to fix it
Return the status that matches the content, from the server:
export async function loader({ params }) {
const post = await getPost(params.slug);
if (!post) throw new Response("Not Found", { status: 404 });
return post;
}For a client-rendered app, the server route has to know the resource is missing (the soft 404 fix). Update a broken internal link, or redirect the old URL permanently (the broken link fix). Regenerate the sitemap from live data (the sitemap fix). Keep the previous release’s hashed assets online while cached HTML may still reference them (the resource fix).
Run the check
squirrel audit https://example.com --rule-include links/broken-links,crawl/sitemap-4xx,crawl/soft-404,images/broken-images,reliability/broken-resourcesA signed-out local audit costs nothing.
Related terms
- Broken link: A link whose target answers with an error, does not resolve, or is malformed.
- Soft 404: A page that tells the visitor it does not exist (or is empty) while the server answers HTTP 200.
- Redirect chain: A sequence of two or more redirects between the requested URL and the final response.