What is a 404 Error? SEO Guide for Beginners

Learn what a 404 error means in SEO, why it matters, and how to fix it to protect your rankings.

A 404 error is an HTTP client error status code that means the server cannot find the page the user or crawler requested. The HTTP specification (RFC 9110, section 15.5.5) defines it precisely: the 404 (Not Found) status code indicates that the origin server did not find a current representation for the target resource or is not willing to disclose that one exists. When someone visits a URL that does not exist on your site, the server returns a 404 response, which typically displays a "Page Not Found" message. This can happen because the page was deleted, the URL was typed incorrectly, or a link pointing to that page has a typo.

One subtlety that trips people up is that a 404 says nothing about whether the page is gone for good. As RFC 9110 puts it, a 404 status code does not indicate whether this lack of representation is temporary or permanent. If you know a page is gone permanently, the spec prefers the 410 (Gone) status code instead. MDN classifies 404 as a client error response in the 4xx range and notes that a 404 response is heuristically cacheable, meaning intermediaries may cache it unless your cache-control headers say otherwise.

Why 404 Errors Matter for SEO

A few 404 errors are normal and Google has confirmed they do not inherently hurt your rankings. Google Search Central is explicit that 404 errors do not harm your site's indexing or ranking, and that you can safely leave them as 404s when there is genuinely nothing to serve. Google also treats 410 (Gone) much the same way it treats 404 for ranking purposes, so the choice between them is about signaling intent, not avoiding a penalty. But when 404 errors pile up, they create real problems. Every 404 page that has external backlinks pointing to it is wasting link equity. That authority goes nowhere instead of boosting your rankings.

404 errors also waste your crawl budget. When Googlebot visits a URL and gets a 404, it spent time and resources on a dead end instead of crawling your actual content. For large sites with limited crawl budget, this inefficiency adds up.

The user experience impact is just as significant. A visitor who clicks a link from another site and lands on a 404 page is likely to leave immediately. That is a potential customer or reader lost because of a broken link you could have fixed.

I once audited a site that had over 2,000 404 errors, many of them on pages that previously had strong backlinks from authoritative domains. All that link equity was evaporating into dead pages. By implementing 301 redirects from those old URLs to relevant current pages, the site saw a 15% increase in organic traffic within six weeks.

How 404 Errors Work

When your server receives a request for a URL, it looks for a matching page or resource. If nothing matches, it returns a 404 HTTP status code. The browser then displays the 404 error page, which is either a default server page or a custom page you have designed.

It is important to understand the difference between a "soft 404" and a real 404. A soft 404 happens when a page returns a 200 (success) status code but displays "page not found" content. Google can detect soft 404s and treats them similarly to real 404s, but the mixed signals can confuse indexing. Always ensure that non-existent pages return an actual 404 status code.

There is also the 410 Gone status code, which explicitly tells search engines that a page has been permanently and intentionally removed. Google deindexes 410 pages faster than 404 pages. If you deliberately removed a page and it is not coming back, 410 is the stronger signal.

Google Search Console tracks 404 errors in its Pages report (formerly Coverage report). You can see which URLs are returning 404s and investigate whether they need redirects, need to be recreated, or are fine as-is.

How to Fix 404 Errors on Your Site

Check Google Search Console regularly - The Pages report shows you all URLs that returned 404 errors during crawling. Sort by the pages that were linked from external sites or had impressions in search results. These are the highest priority to fix because they had SEO value.
Redirect 404 pages that had backlinks - Use Ahrefs, Moz, or Google Search Console to identify 404 URLs that still have external backlinks. Set up 301 redirects from those URLs to the most relevant existing page on your site to recapture that link equity.

Create a useful custom 404 page - Design a 404 page that helps users find what they were looking for. Include a search bar, links to popular pages, and a clear message explaining the page was not found. A good 404 page recovers users who would otherwise bounce immediately.

Fix internal broken links - Use Screaming Frog or a site audit tool to find any links within your own site that point to 404 pages. Broken internal links waste crawl budget and create dead ends for users navigating your site. Update or remove these links.

Prevent future 404 errors during URL changes - Any time you change a page's URL, delete a page, or restructure your site, create 301 redirects from the old URLs to the new ones before making the change. Being proactive is far easier than cleaning up a mess after the fact.

Common Mistakes to Avoid

Redirecting all 404s to the homepage: This is lazy and Google treats it as a soft 404. If someone was looking for a specific blog post and gets sent to the homepage, that is a terrible user experience and Google knows it. Always redirect to the most relevant specific page.
Ignoring 404 errors because "Google says they are fine": While Google says 404s are not a direct ranking factor, pages with backlinks that return 404 are absolutely losing value. The lost link equity is a real SEO cost. Prioritize fixing 404 pages that have inbound links.
Creating soft 404 pages that return a 200 status code: If a page shows "content not found" but returns a 200 status, Google has to guess whether it is a real page or an error. This wastes crawl budget and creates indexing confusion. Non-existent pages must return a 404 or 410 status code.

In Practice

Say you deleted an old pricing page at /old-pricing and the URL no longer maps to anything. The wrong move is to let your CMS quietly serve your homepage at that address with a 200 status, which is a soft 404. The right move depends on intent.

If the page is permanently gone with no replacement, return a real 410 so Google deindexes it faster. In Nginx that is one line:

location = /old-pricing {
    return 410;
}

If there is a relevant replacement, send a 301 redirect to recapture the link equity instead:

location = /old-pricing {
    return 301 /pricing;
}

You can confirm the server is actually returning the status you intend with a header check. A genuine 404 looks like this:

$ curl -sI https://example.com/this-page-does-not-exist
HTTP/2 404
content-type: text/html; charset=UTF-8

The number after HTTP/2 is the part that matters to crawlers. If that line reads HTTP/2 200 for a page that displays "not found" text, you have a soft 404 and need to fix the status code, not the wording.

What is an HTTP Status Code? covers the full family of response codes that 404 belongs to.
What is a 410 Gone Error? explains the stronger signal for pages you have permanently removed.
What is a 301 Redirect? shows how to recapture link equity from a dead URL that has a replacement.
What is Index Coverage? describes the report where soft 404s surface when a missing page returns 200 instead of 404.
What is Crawl Budget? explains why piles of 404s and soft 404s waste Googlebot's limited crawling on dead ends.

Key Takeaways

A 404 error means the server cannot find the requested page. A few are normal, but excessive 404s waste crawl budget and link equity.
The highest-priority 404s to fix are those that have external backlinks pointing to them. Redirect these to relevant pages to recapture authority.
Create a helpful custom 404 page with search and navigation to recover users who hit dead ends.
Monitor Google Search Console's Pages report regularly to catch and fix 404 errors before they accumulate.