Understanding 404 Errors: Causes, Fixes, and SEO Impact

One of the most common errors users encounter online is the "404 not found" error. If you've spent time browsing the internet, you've almost certainly seen it, often after clicking a link or trying to access a page that no longer exists.

A 404 error occurs when a user's browser successfully connects to a website’s server, but the server cannot locate the specific page or file requested. Unresolved or widespread 404 errors can frustrate users and limit access to valuable content that requires time and resources to create. For website owners, addressing these errors is important for maintaining a healthy website and a positive user experience.

In this guide, we explain what causes HTTP 404 errors, how they affect SEO and usability, and the most effective ways to identify and fix them.

What is a 404 not found error?

A 404 error occurs when a user attempts to access a webpage or resource on a website, and the server receives the request, but the requested URL does not exist. In other words, the site is reachable, but the content is not. Users typically see a message such as “The page you’re looking for doesn’t exist” or come across a custom 404 error page when this happens.

A 404 error is an HTTP status code that indicates a missing or unavailable resource rather than a problem with the server itself. These errors are part of a broader group of HTTP client error responses that prevent a webpage from being displayed. Related status codes include:

• Error 400, which indicates an invalid request
• Error 401, which indicates authentication is required
• Error 402, which indicates that a payment is required to process the request
• Error 403, which indicates that the server understands the request, but the user is not authorized to access the resource

There are several common scenarios that can trigger a 404 status code. These include mistyped URLs, pages that have been moved or deleted without proper redirects, broken internal or external links, and changes to site structure or server configuration.

How do you find 404 errors on your website?

404 errors can appear in a variety of ways, and website owners often discover them only after users begin encountering broken pages. Proactively identifying page not found errors on your own website helps ensure it remains accessible, functional, and easy for users and search engines to navigate.

Website owners can detect 404 errors more reliably by using a combination of tools and reports, including:

• Google Search Console. This free tool enables website owners to monitor their site's performance and includes a "Coverage" report, where you can see URLs that are returning 404 errors for Google.
• Google Analytics. GA4 can provide helpful insights into 404 error reports. You can set up custom alerts to notify you when there is a significant increase in 404 errors on your website. Using the tool to analyze user behavior data can also provide clues about where users are encountering errors and help you prioritize fixing them.
• Third-party website auditing tools. These can be a big help in detecting 404 errors. Tools like SEMrush, Ahrefs, and Moz offer features for crawling your website and detecting broken links, including 404 errors. They also provide detailed reports, including information about the URLs that are returning 404 errors, the pages linking to them, and suggestions for fixing the issues. Crawlers like Screaming Frog can run full site crawls to find any instances of internal or external broken links.

What are the SEO implications?

If a search engine consistently encounters a 404 error when attempting to crawl a URL, the URL will likely be removed from the search engine's index. This is expected behavior and not inherently harmful, but it can become a problem and have a negative impact on SEO when important or high-value pages return 404 errors unexpectedly.

Additionally, excessive 404 errors can waste crawl budget, especially on larger sites. Search engine crawlers can spend resources crawling non-existent pages instead of discovering and indexing valuable content. While occasional 404s are normal, addressing recurring or high-impact errors helps ensure crawl resources are used efficiently.

How to manage and fix 404 errors

404 error codes can affect both search visibility and user experience when they occur on important pages or internal links. Once you’ve identified them on your website, the next step is to address them. The right fix or action depends on why the page is missing and whether users or search engines are still trying to access it.

Check and update URL permalinks

Make sure that your website's permalinks are set correctly and match the URLs of your pages. Incorrect or changed permalink settings can cause valid pages to return a 404 status.

Redirect moved or deleted pages accordingly

If you've permanently moved or deleted a page, use a 301 redirect to permanently redirect users and search engines to the new URL or alternative content.

Check your .htaccess file

Check your .htaccess file for any misconfigurations or directives that might be causing pages to return 404 errors. You can also use the .htaccess file to manage redirects and customize error-handling settings.

Verify file and directory permissions

404 errors are sometimes caused by file and directory permissions on your server that are not configured correctly. Make sure that these permissions are properly configured to allow access to authorized users and visitors.

Use broken link scans to manually fix issues

Use the broken link scans discussed earlier to identify internal links on your site that lead to missing pages. Once identified, review the affected content and manually update it by replacing broken links with valid URLs or removing them entirely if the links are no longer relevant.

Check recent software updates

In some cases, 404 errors can occur if a broken plugin is installed on your website. To avoid this, be sure to promptly apply software updates and remove any suspicious-looking plugins or themes, as they can result in errors and even malware.

How to troubleshoot temporary or user-side issues

These steps help determine whether the issue is temporary or specific to a user.

• Clear your cache. Cached versions of web pages can sometimes lead to 404 errors if they are outdated or corrupted. Clearing your cache will ensure you're using the most up-to-date version of the website. And, if it doesn't fix the error, it will at least confirm that the problem isn't caused by cached data on your end.
• Refresh broken pages. Refreshing broken pages or trying to access them in a different browser can sometimes resolve 404 errors caused by temporary glitches or a website server that is simply too busy to fulfill the request.

Handle expected 404 errors properly

Sometimes a 404 error is the correct response. In this case, you should create a custom 404 page that will be displayed anytime a user encounters this situation. This page should provide helpful information and navigation options to users, helping you maintain a positive user experience in the face of an otherwise frustrating situation.

Take a proactive approach to website management

The most effective way to handle 404 errors is to take a proactive approach. Regular site audits, broken link checks, and ongoing monitoring help catch missing pages early and reduce their impact on user experience and search visibility. Addressing issues quickly and using redirects or custom 404 pages when appropriate helps keep your site accessible and easy to navigate.

Because technical issues and security problems can also contribute to unexpected errors, proactive site maintenance should be part of any website management process. SiteLock’s website security scanning solutions support ongoing site health by detecting vulnerabilities, identifying malware, and helping prevent issues that can lead to broken pages or site instability.