What Are 4xx Errors?

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4xx errors indicate an error in the request by the client or browser. Most commonly, a broken link or link referring to a page that is no longer available leads to a 404 “Not Found” error. While there are 29 official 4xx error codes, webmasters most frequently experience these error codes:

• 403 Forbidden – the server has determined that the client does not have permission to access the URL 
• 404 Not Found – the requested URL is not currently available but may be available in the future
• 410 Gone – the requested URL is no longer available and will not be available again

4xx errors can cause content to be excluded from search engine indices and therefore ineligible for inclusion in search results.

As links are the primary point of reference for search engines in crawling, indexing and ranking content in their results, links that refer to URLs returning 4xx errors are often worth fixing. Common solutions are to:

• Update links to point to valid URLs
• Set 301 redirects to refer users and crawlers to a suitable replacement page or resource
• Replace a resource that should be available at the requested URL (was mistakenly moved or deleted)

When is a 4xx Error OK? 

There are many cases where 4xx errors are OK and preferable. 

• A 404 Not Found status to indicate that an item has become temporarily unavailable (e.g. a product out of stock or an event with no current dates scheduled)
• A 451 Unavailable for Legal Reasons status to indicate a page has been removed for legal reasons (e.g. a copyright claim requires that content is removed from a website)
• A 429 Too Many Requests status, often served to clients requesting too many pages too quickly (e.g. automated bots that can bog down server with rapid requests)

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