What is a 404 error in SEO?

What is a 404 Error in SEO? A Comprehensive Guide

In the intricate world of Search Engine Optimisation (SEO), where every click and every page load contributes to a website’s success, encountering a “404 Not Found” error can feel like hitting a brick wall. Far from being a mere technical glitch, a 404 error, if left unaddressed, can significantly impact a website’s SEO performance, user experience, and ultimately, its bottom line. But what exactly is a 404 error, and why is it so crucial for SEO professionals to understand and manage them effectively? Let’s delve into the depths of this common yet often misunderstood issue.

Understanding the Basics: What is a 404 Error?

At its core, a 404 error is an HTTP status code, a three-digit number that a web server sends back to a web browser (or a search engine crawler) to indicate the status of a request. When you type a URL into your browser or click on a link, your browser sends a request to the web server hosting that website. The server then responds with a status code.

A 404 status code specifically means “Not Found.” This signifies that the server could not find the requested resource. In simpler terms, the web page, image, document, or any other file you were trying to access doesn’t exist at the specified URL. It’s like trying to find a book on a library shelf, only to discover that the shelf is empty where the book should be.

It’s important to distinguish a 404 error from other HTTP status codes:

• 200 OK: Everything is working perfectly, and the requested resource was found and delivered successfully.
• 301 Permanent Redirect: The requested resource has permanently moved to a new URL. This is a crucial code for SEO as it passes on most of the link equity (or “link juice”) to the new location.
• 302 Found (Temporary Redirect): The requested resource has temporarily moved to a new URL. This typically doesn’t pass as much link equity as a 301.
• 500 Internal Server Error: Something has gone wrong on the server’s side, preventing it from fulfilling the request. This is a more severe issue than a 404.

Why Do 404 Errors Occur? Common Causes

404 errors can arise for a multitude of reasons, some accidental, others due to website restructuring:

• Typographical Errors: The most common cause. A user might misspell a URL, or a link on another website might contain a typo.
• Deleted Pages: Content is often removed from websites for various reasons – it might be outdated, irrelevant, or part of a content audit. If the page isn’t properly redirected after deletion, it will result in a 404.
• Moved Pages Without Redirects: When a page’s URL is changed (e.g., during a website redesign or content reorganisation), if a 301 redirect isn’t implemented from the old URL to the new one, any attempt to access the old URL will lead to a 404.
• Broken Internal Links: Links within your own website that point to non-existent pages. This could be due to errors during content creation or pages being moved/deleted without updating internal links.
• Broken External Links (Inbound Links): Other websites linking to your pages that no longer exist or have changed URLs without your knowledge.
• Incorrectly Configured Servers: Less common, but server misconfigurations can sometimes lead to erroneous 404 responses.
• Expired Domain Names: If a domain name expires and the website is taken down, all URLs associated with it will result in 404s (or a domain parking page).

The SEO Impact of 404 Errors: Why They Matter

While a single 404 error might seem insignificant, a collection of them can have a detrimental effect on your SEO efforts and overall website performance.

1. Negative User Experience

This is perhaps the most immediate and tangible impact. When a user clicks on a link expecting to find information and is met with a “Page Not Found” message, it’s frustrating. A poor user experience can lead to:

• Increased Bounce Rate: Users quickly leave your site, indicating to search engines that your site might not be relevant or helpful.
• Reduced Time on Site: Less engagement translates to lower perceived value.
• Decreased Conversions: If users can’t find what they’re looking for, they certainly won’t be completing purchases or filling out forms.
• Damaged Brand Reputation: A website riddled with broken links appears unprofessional and unreliable.

2. Wasted Crawl Budget

Search engine crawlers (like Googlebot) have a “crawl budget” – a finite amount of resources they allocate to crawling your website. When a crawler encounters numerous 404 errors, it wastes its crawl budget on non-existent pages instead of discovering and indexing your valuable, existing content. This can lead to:

• Slower Indexing of New Content: New pages might take longer to be discovered and appear in search results.
• Missed Opportunities: Important pages might not be crawled as frequently, potentially affecting their ranking.

3. Loss of Link Equity (Link Juice)

This is a critical SEO concern. When other websites link to your content, they pass on “link equity” or “link juice,” which is a signal of authority and trustworthiness to search engines. If these inbound links point to 404 pages:

• The Link Equity is Lost: The power of those valuable backlinks simply vanishes into thin air, as there’s no page to receive it.
• Reduced Ranking Potential: Your pages that should be benefiting from these links are not, potentially hindering their ability to rank higher in search results.

4. Eroded Keyword Rankings

If pages that were previously ranking for specific keywords suddenly disappear and result in 404s, those rankings will inevitably drop. This means a loss of organic traffic and visibility for those keywords.

5. Impact on Site Structure and Internal Linking

A well-optimised website has a logical internal linking structure. 404 errors within your internal links break this structure, making it harder for both users and search engines to navigate your site and understand its hierarchy.

How to Identify and Fix 404 Errors for SEO

Proactive identification and effective resolution of 404 errors are paramount for maintaining a healthy SEO profile.

Identification Tools:

• Google Search Console (GSC): This is your primary tool. Under “Indexing” > “Pages,” GSC will list “Not found (404)” errors. It shows you the URLs that Googlebot has tried to crawl and found to be missing. This is invaluable for understanding how Google perceives your site.
• SEO Crawling Tools: Tools like Screaming Frog SEO Spider, Ahrefs Site Audit, Semrush Site Audit, and Moz Pro have site crawling capabilities that can identify all 404 errors on your website (both internal and external links pointing to 404s).
• Website Analytics (e.g., Google Analytics): While not directly showing 404s as errors, you can often identify pages with unusually high bounce rates or short average session durations, which might indicate a hidden 404 issue if users are landing on a custom 404 page.

Fixing 404 Errors: The SEO-Friendly Approach

Once identified, fixing 404 errors isn’t just about making them disappear; it’s about doing so in a way that benefits your SEO.

1. Implement 301 Redirects (Permanent Redirects): This is the gold standard for fixing 404s, especially for pages that have moved or been deleted but still have value (e.g., incoming links, traffic).
   • To a Relevant New Page: If the content has moved, redirect the old URL to the new, updated URL.
   • To a Relevant Category Page: If a specific product page is deleted, but similar products exist, redirect to the relevant category page.
   • To the Homepage (Use with Caution): Only use this as a last resort if there is absolutely no relevant alternative. Redirecting too many unrelated 404s to the homepage can be seen as “soft 404s” by Google and dilute user experience.
   • How to implement: This typically involves editing your .htaccess file (for Apache servers), using server-side configurations, or employing redirect plugins/functionality within your Content Management System (CMS) like WordPress.
2. Correct Internal Links: If your site’s internal links are pointing to 404 pages, update them to point to the correct, existing URLs. This improves user navigation and crawlability.
3. Update External Links (Where Possible): While you can’t directly control other websites, if you notice a prominent website linking to a 404 on your site, consider reaching out to them and requesting they update the link to a correct page. This helps regain lost link equity.
4. Create a Custom 404 Page: Even with the best efforts, some 404s are inevitable (e.g., user typos). A well-designed custom 404 page can mitigate the negative user experience.
   • Be User-Friendly: Apologise for the inconvenience, explain that the page wasn’t found, and offer helpful alternatives.
   • Include Search Bar: Allow users to search your site for the content they were looking for.
   • Provide Navigation Options: Include links to your homepage, popular categories, sitemap, or contact page.
   • Maintain Branding: Ensure the 404 page visually aligns with the rest of your website.
   • Avoid Excessive Links: Don’t overwhelm the user with too many options.
5. Recreate Deleted Content (If Beneficial): If a deleted page was highly valuable and generated significant traffic or links, consider recreating the content or a similar version and then implementing a 301 redirect from the old URL to the new one.

Soft 404s: A Stealthy Problem

It’s crucial to understand “soft 404s.” A soft 404 occurs when a server responds with a 200 OK status code (meaning the page exists), but the content on the page clearly indicates that the requested resource was not found. For example, a page might display “Page not found” or “Product unavailable” while still returning a 200 status.

From a user’s perspective, it looks like a 404. From a search engine’s perspective, it looks like a valid page, wasting crawl budget and potentially causing issues:

• Google Will Eventually Treat it as a 404: Google is sophisticated enough to recognise soft 404s and will eventually de-index them. However, in the interim, it consumes crawl budget.
• Confusing for Search Engines: It provides conflicting signals, which can hinder proper indexing.

How to Fix Soft 404s: Ensure that pages that genuinely don’t exist return a proper 404 (or 410 Gone) status code. If a product is out of stock, for example, it’s better to display an “Out of Stock” message on a 200 OK page rather than misleadingly suggesting the page doesn’t exist.

Conclusion: A Continuous Process

Managing 404 errors is not a one-off task; it’s a continuous process that requires vigilance and regular auditing. As your website evolves, pages will be added, moved, and removed. By understanding the causes, implementing effective identification strategies, and applying SEO-friendly fixes, you can minimise the negative impact of 404 errors on your website’s performance. Prioritising a clean, well-maintained site structure not only pleases search engine crawlers but, more importantly, provides a seamless and positive experience for your valuable users, ultimately driving better SEO results. So, next time you see that “404 Not Found” message, remember it’s not just an error code – it’s a signal to take action for the health of your website.