What are 400 errors on a website?

400 errors are HTTP client-side errors returned when a browser or crawler makes a request the server cannot fulfil. The most common is 404 Not Found — the page does not exist. Others include 403 Forbidden (access denied), 401 Unauthorised (login required), 410 Gone (permanently deleted) and 429 Too Many Requests (rate limited). They tell Google the page is broken or inaccessible.

What are 500 errors on a website?

500 errors are HTTP server-side errors. Unlike 400 errors — which are the client's fault — 500 errors mean something went wrong on your server. Common ones include 500 Internal Server Error (generic crash), 502 Bad Gateway (upstream server problem), 503 Service Unavailable (server overloaded or in maintenance) and 504 Gateway Timeout (upstream took too long to respond).

Do 400 and 500 errors hurt SEO?

Yes. 404 errors waste crawl budget — Googlebot visits the broken URL and gets nothing useful. If important pages return 404, they drop out of the index. 410 Gone tells Google to remove the URL immediately. 500 errors are even more damaging: if Google crawls your site during a 500 error, it may temporarily deindex those pages. Persistent 503 errors signal an unreliable site. All of these reduce your rankings.

How do I find all 400 and 500 errors on my website?

The most thorough method is an HTTP error audit — a crawler that visits every page on your site and records the HTTP status code returned. You can run one at https://dev.aiwebpageseo.com/performance-tools.html#http-error-audit for sites from 10 pages up to 1,000 pages. The audit shows you every broken URL, what error code it returns, and which page linked to it — so you know exactly what to fix.

What is the difference between a 404 and a 410 error?

A 404 Not Found tells search engines the page does not exist right now — but it might come back. Google will keep checking. A 410 Gone is a permanent signal: the page is gone and will never return. Use 410 when you deliberately delete a page and do not plan to redirect it. Google processes 410 removals faster than 404s.

How do I fix a 404 error?

First decide if the page should exist. If yes — restore it or recreate the content. If no — set up a 301 permanent redirect to the most relevant existing page. If the page had no value, return a clean 410 Gone. Never leave important URLs returning 404 without a redirect — you lose all the link equity that URL had accumulated.

How do I fix a 500 error?

500 errors require server-side investigation. Check your server error logs immediately — they will show the exact line of code or configuration that failed. Common causes include database connection failures, PHP or Node.js crashes, misconfigured .htaccess files, memory limit exceeded, or a failed plugin or dependency. If the error is intermittent, check your server's memory and CPU under load.

How often should I audit my website for HTTP errors?

For small sites (under 50 pages) — monthly is sufficient. For medium sites (50–500 pages) — weekly, especially after any CMS update, plugin change, or content migration. For large sites (500+ pages) — continuously, ideally as part of an automated monitoring workflow. Every deployment or structural change to your site is a risk for new 404s.

What is a soft 404 and why does it matter?

A soft 404 is when a page returns an HTTP 200 OK status but displays a 'page not found' message in the content. Search engines see 200 and index the page — but users land on a useless error page. Google detects soft 404s and may deindex them. Fix them by returning a proper 404 or 410 status code, or by redirecting to relevant content.

Can I check HTTP errors on a large site with thousands of pages?

Yes. The HTTP Error Audit at dev.aiwebpageseo supports scans up to 1,000 pages for £9.99 — covering large e-commerce sites, agency client sites and content-heavy domains. Results are filterable by error type (4xx, 5xx, redirects) and exportable as CSV. See https://dev.aiwebpageseo.com/performance-tools.html#http-error-audit

How to Find Every 400 & 500 Error on Your Website

HTTP errors silently damage your SEO every day. Google crawls your site, hits a 404 or a 500, and leaves empty-handed — wasting crawl budget, losing rankings, and sending users to dead ends. Here is everything you need to know about finding and fixing them.

🔴 Run HTTP Error Audit All Performance Tools →

What are 400 and 500 HTTP errors?

Every time a browser or search engine requests a page from your server, the server responds with a three-digit status code. Codes starting with 4 are client errors — the request was wrong or the page does not exist. Codes starting with 5 are server errors — something broke on your end.

Common 4xx errors

Code	Name	What it means	SEO impact
404	Not Found	Page does not exist	Wastes crawl budget, removes page from index
410	Gone	Page permanently deleted	Faster deindex than 404 — use intentionally
403	Forbidden	Access denied	Google cannot crawl the page — treated like a soft block
401	Unauthorised	Login required	Page will not be indexed
408	Request Timeout	Server took too long to respond	Googlebot may abandon and not return
429	Too Many Requests	Rate limited	Googlebot backs off — can slow down full crawl

Common 5xx errors

Code	Name	What it means	SEO impact
500	Internal Server Error	Generic server crash	Page may be deindexed if persistent
502	Bad Gateway	Upstream server failed	Signals unreliable infrastructure to Google
503	Service Unavailable	Server overloaded or in maintenance	Temporary — Google retries. Persistent = deindex risk
504	Gateway Timeout	Upstream took too long	Same as 503 — retry behaviour from Googlebot

Do 400 and 500 errors hurt your SEO?

Yes — and in multiple ways.

Crawl budget waste

Google allocates a crawl budget to every site — a limit on how many pages it will crawl in a given period. Every 404 Googlebot visits is a wasted crawl. On large sites with hundreds of broken URLs, this means important pages get crawled less often or not at all.

Lost rankings

If a page that previously ranked starts returning 404, Google will eventually remove it from the index. Any backlinks pointing to that URL stop passing authority. If you do not redirect the URL, those rankings and that link equity are gone.

Poor user experience

Users who land on a 404 page leave immediately. High bounce rates on error pages are a negative user experience signal. On e-commerce sites, a 404 on a product page means a lost sale.

The hidden problem: Most 404s are not on your homepage or main pages — they are buried deep in your site, linked from blog posts, old category pages or external backlinks. You will never find them by browsing. You need a crawler.

How do you find all HTTP errors on your site?

There are three main methods — ranked by thoroughness:

1. HTTP Error Audit tool (fastest and most complete)

The HTTP Error Audit at dev.aiwebpageseo crawls your entire site, follows every internal link, and records the HTTP status code returned by each page. Results are shown in a filterable table — filter by 4xx errors, 5xx errors, redirects, or 200 OK. You can export to CSV for a full report.

It works by starting at your homepage, extracting all internal links, visiting each one, and repeating — exactly as Googlebot does. The scan size is tiered by number of pages:

Scan size	Best for	Cost
10 pages	Small sites, landing pages, quick checks	10p
50 pages	Blogs, small business sites	50p
100 pages	Medium sites, e-commerce stores	£5.00
1,000 pages	Large sites, agencies, full domain audits	£9.99

2. Google Search Console

Google Search Console's Coverage report shows pages returning 404 or other errors that Googlebot has encountered. The limitation: it only shows pages Google has already tried to crawl. New broken pages may take days or weeks to appear. It also does not show errors on pages that are not yet in Google's index.

3. Server error logs

Your web server logs every request and its status code. Parsing your NGINX or Apache access logs will reveal every 4xx and 5xx response across all traffic — not just Googlebot. The downside is that logs require technical access and manual processing, and they do not show you which pages linked to the broken URLs.

Tip: Use the HTTP Error Audit for a complete picture of what a crawler sees right now, and Google Search Console to track what Google has already encountered. The two tools complement each other.

How do you fix 400 and 500 errors?

Fixing 404 errors

For each 404 you find, you have four options:

Restore the page — if it was deleted by mistake, put it back.
301 redirect — if the content moved, redirect the old URL to the new one permanently. This passes link equity.
410 Gone — if the page had no value and you want Google to remove it quickly, return a 410 instead of 404.
Remove the link — if the 404 is caused by an internal link pointing to a non-existent page, update or remove that link.

Fixing 500 errors

500 errors are server-side — check your error logs immediately. Common causes and fixes:

500 Internal Server Error — check PHP/Node error logs. Usually a code exception, memory limit or bad configuration.
502 Bad Gateway — your NGINX or proxy cannot reach the upstream app. Check if your Node/PHP process is running.
503 Service Unavailable — server is overloaded. Add a Retry-After header during planned maintenance. Scale resources for load spikes.
504 Gateway Timeout — upstream is too slow. Increase proxy timeouts or optimise database queries causing slow responses.

After fixing: Re-run the HTTP Error Audit to confirm the errors are resolved. For 301 redirects, check the Redirects filter in the results to confirm the redirect is working and the destination returns 200.

How often should you audit for HTTP errors?

The right frequency depends on how often your site changes:

Small sites (under 50 pages) — monthly is sufficient unless you publish frequently.
Medium sites (50–500 pages) — after every deployment, CMS update or content migration. Weekly for active sites.
Large sites (500+ pages) — continuous monitoring. Every structural change risks new 404s. Run a full 1,000-page audit after any major changes.
After any site migration — always run a full audit immediately after moving to a new domain, CMS or hosting provider.

What is a false 200 status and why does it hurt SEO?

Some websites return an HTTP 200 OK status on pages that have no real content — for example an empty search results page or a CMS that serves a generic placeholder when a URL does not match any content. Google treats these as low-quality pages and may exclude them from its index.

Common scenarios where this occurs:

A CMS that returns HTTP 200 on every URL regardless of whether content exists
Search results pages with zero results that still return HTTP 200
Thin pages with minimal content that do not satisfy the search intent

The fix is to ensure every URL either returns real content with HTTP 200, redirects to a relevant page with HTTP 301, or returns HTTP 404 or 410 if the content genuinely does not exist.

🔴 Find every error on your site right now

Run the HTTP Error Audit and get a complete list of every 4xx and 5xx error across your site — filtered, sortable, and exportable as CSV. From 10p for small sites up to £9.99 for 1,000 pages.

Run HTTP Error Audit →

How to Find Every 400 & 500 Error on Your Website

What are 400 and 500 HTTP errors?

Common 4xx errors

Common 5xx errors

Do 400 and 500 errors hurt your SEO?

Crawl budget waste

Lost rankings

Poor user experience

How do you find all HTTP errors on your site?

1. HTTP Error Audit tool (fastest and most complete)

2. Google Search Console

3. Server error logs

How do you fix 400 and 500 errors?

Fixing 404 errors

Fixing 500 errors

How often should you audit for HTTP errors?

What is a false 200 status and why does it hurt SEO?

🔴 Find every error on your site right now

Related tools

About dev.aiwebpageseo