Page Not Found: A Guide to HTTP Error Codes
Everything you need to know about HTTP error codes, including what they mean, why they happen, and how to fix them.
- HTTP error codes signal problems in the communication between your browser and a website’s server.
- Status codes are grouped into five classes, with 4xx errors indicating client-side issues and 5xx errors indicating server-side problems.
- Common errors such as 404 Not Found and 500 Internal Server Error can often be resolved using simple troubleshooting steps.
HTTP error codes are three-digit responses that show how a server responds to a browser’s request. They’re part of the HTTP request-response cycle, the process that happens every time a browser loads a webpage, image, or file from a website. Each request you make, whether by clicking a link or entering a URL, prompts the server to reply with a status code that explains what happened with that request.
You can think of this exchange as a digital handshake between your browser and a website’s server. When everything works properly, the server returns a success response, confirming that the content was delivered. When something goes wrong, the server returns an error code that explains the issue, such as a missing page, a permissions problem, or a server failure. Understanding these codes helps you quickly identify whether an issue is caused by a simple mistake, a client-side request problem, or a server-side malfunction, making troubleshooting faster and more effective.
Quick Answer
HTTP error codes are three-digit numbers a server returns during the request-response cycle to indicate whether a web page loaded successfully or failed due to an issue.
Here’s a quick guide to what those codes could indicate:
- 2xx codes: Success (the request worked)
- 3xx codes: Redirection (the page moved)
- 4xx codes: Client error (problem with the request, like 404 Not Found)
- 5xx codes: Server error (problem on the website’s server, like 500 Internal Server Error)
Watch: Why You See “Page Not Found” Errors Online
Short on time? Watch our video for a clear overview of HTTP error codes, what causes the most common client-side and server-side errors, and the practical steps visitors and website owners can take to troubleshoot them quickly.
HTTP Status Code Cheat Sheet
Having a quick summary of the most common HTTP error codes can save you time when troubleshooting a broken web page. Use this reference table to immediately identify the meaning and origin of the error you are encountering.
| Code | Meaning | Type |
|---|---|---|
| 200 | OK | Success |
| 301 | Moved permanently | Redirection |
| 403 | Forbidden | Client error |
| 404 | Not sound | Client error |
| 500 | Internal server error | Server error |
| 502 | Bad gateway | Server error |
Understanding Status Classes
HTTP status codes are grouped into five distinct classes based on their first digit. This structure makes it easier to quickly understand whether a request is working correctly, still in progress, or has failed due to a client or server issue.
- 1xx (Informational): The request was received and is still being processed.
- 2xx (Success): The request was successfully completed, and the content was delivered.
- 3xx (Redirection): The requested resource has moved, and further action is required to reach it.
- 4xx (Client error): The request contains an issue such as an incorrect URL, missing permissions, or invalid input.
- 5xx (Server error): The server failed to complete a valid request due to an internal problem.
4xx and 5xx codes are similar but differ based on the root cause.
- 4xx errors indicate a problem with the client-side request, such as the browser or user input.
- 5xx errors indicate a server-side problem, meaning the website or hosting environment failed to process the request correctly.
1xx: Informational Responses
Informational responses are temporary status codes indicating that the server is still processing the request. Because these occur in the background during the connection phase, standard internet users rarely see them displayed on their screens.
- 100 Continue: The initial part of the request was received, and the client should proceed with sending the rest.
- 101 Switching Protocols: The server accepts the client’s request to change the communication protocol.
2xx: Success Codes
Success codes confirm that the digital handshake was completed without issue. When everything works, these codes are generated invisibly, allowing text, videos, and images to load without interruption.
- 200 OK: The standard response for a successful HTTP request. It means the requested page loaded correctly.
- 201 Created: The request was successful, and a new resource was created as a result.
3xx: Redirection Codes
Redirection codes tell your browser that the resource it requested has been moved. Your browser automatically follows the new path, which helps when website administrators update link structures or migrate domains.
- 301 Moved Permanently: The requested URL has moved permanently to a new location. This redirects visitors seamlessly and passes SEO authority to the new page.
- 302 Found: The resource is temporarily located elsewhere, but future requests should still use the original address.
4xx: Client Error Codes
4xx errors occur when the request sent by the browser cannot be fulfilled because of a client-side issue, such as an incorrect URL or insufficient permissions. This means the problem is on your end, such as a mistyped URL or insufficient authorization. These client-side errors block access to the target page, but they are often straightforward to fix with basic troubleshooting.
403 Forbidden Error
A 403 Forbidden error means you do not have permission to view the requested files or directories. The web server understands your request but is refusing to grant access.
Common causes include:
- Missing or incorrect file permissions
- Restricted directory access
- IP blocking or firewall rules
- Missing or invalid login credentials
How to Fix a 403 Forbidden Error
The steps to fix this error vary depending on who is intending to access the website.
For Visitors:
If you’re trying to access a website, try the following:
- Log in to the website if authentication is required.
- Clear your browser cache and cookies.
- Disable your VPN or proxy service and try again.
- Double-check that you’re visiting the correct URL and not a restricted directory.
For Webmasters:
If you manage the website, check the following:
- Review file and folder permissions.
- Check your .htaccess file or other security rules for access restrictions.
- Verify that authentication and authorization settings are configured correctly.
- Ensure the directory contains a valid default index file (such as index.html or index.php).
404 Not Found Error
A 404 Not Found error occurs when the server cannot locate the requested page. This typically happens because the content was deleted, the page was moved without a redirect, or the visitor typed the URL incorrectly. Unresolved 404s can quickly degrade a site’s user experience.
How to Fix a 404 Not Found Error
- For Visitors: Double-check the URL for spelling mistakes. Try using the website’s search bar to find the content, or navigate up one directory level in the address bar.
- For Webmasters: Use site auditing tools to identify broken links. Set up a custom 404 page to guide lost visitors back to your home page, and implement 301 redirects for any deleted or moved content.
What Are Soft 404s and How They Impact SEO
A soft 404 occurs when a webpage displays a “Page Not Found” or similar error message to visitors but returns a 200 OK HTTP status code instead of a proper 404 Not Found or 410 Gone response. While users recognize that the page is unavailable, search engines interpret the 200 OK status as a successful page load.
This can create several SEO issues, including:
- Search engines indexing empty or low-value pages
- Wasted crawl budget on pages that no longer provide useful content
- Reduced overall site quality signals, which can negatively impact search visibility
How to Fix Soft 404s
If a page has been permanently removed and no suitable replacement exists, configure your server to return a 404 Not Found or 410 Gone status code. If the content has moved to a new location, implement a 301 Moved Permanently redirect to send users and search engines to the correct page. This helps search engines understand the status of your content and maintain a healthy, well-optimized website.
5xx: Server Error Codes
Whenever you encounter a 5xx code, the fault lies with the website’s server. These server-side HTTP error codes indicate that your request was valid, but the host encountered an internal issue that prevented successful delivery.
500 Internal Server Error
A 500 Internal Server Error is a generic server-side response indicating that the server encountered an unexpected condition while processing an otherwise valid request.
Common causes include:
- Faulty or incompatible plugins and themes
- Exhausted server memory or resource limits
- Broken scripts or application errors
- Incorrect server configuration or file permissions
How to Fix a 500 Internal Server Error
Next steps for fixing this issue will depend on who is looking to access the page.
For Visitors:
If you’re trying to access a website, try the following:
- Refresh the page after a few minutes.
- Clear your browser cache and cookies.
- Try accessing the page again later, as the issue may be temporary.
For Webmasters:
If you manage the website, check the following:
- Review your server error logs to identify the source of the problem.
- Disable recently installed or updated plugins and themes to isolate software conflicts.
- Verify your scripts and configuration files for syntax or configuration errors.
- Restart server or application processes if necessary and confirm the hosting environment has sufficient resources.
502 Bad Gateway Error
A 502 Bad Gateway error occurs when a server acting as a gateway or proxy receives an invalid response from an upstream server. This often happens during traffic spikes or with complex firewall routing issues.
Common causes:
- Server overload or traffic spikes
- Broken CDN or proxy configuration
- Firewall or routing issues
- Backend server downtime
How to Fix a 502 Bad Gateway Error
Similar to a 500 Internal Server Error, you’ll follow different steps based on who needs to access the site.
For Visitors:
- Refresh or retry after a few minutes
- Try a different browser or incognito mode
- Switch DNS servers if issues persist
For Webmasters:
- Check CDN configuration
- Restart backend services
- Review server logs and upstream connectivity
- Investigate traffic spikes or routing failures
Mastering Website Maintenance
Understanding HTTP error codes is essential for diagnosing website issues and maintaining a reliable online experience. These three-digit status codes provide valuable information about what happened during the communication between a browser and a server, making it easier to determine whether a problem originates from the client or the website itself.
Whether you’re troubleshooting a 404 Not Found error, resolving a 500 Internal Server Error, or configuring redirects after moving content, knowing what each status code means can save time and reduce frustration. For website owners, regularly monitoring and resolving 4xx and 5xx errors improves user experience, maintains search engine visibility, and ensures visitors can access important content without interruption. By understanding how HTTP status codes work and following troubleshooting best practices, you can keep your website running smoothly and provide a more dependable browsing experience.
Frequently Asked Questions About HTTP Status Codes
What are the most common HTTP error codes?
The most common HTTP error codes are 404 Not Found, 500 Internal Server Error, 403 Forbidden, and 502 Bad Gateway. A 404 indicates that a page cannot be found, while a 403 means access to the requested resource is forbidden. A 500 signals a general server malfunction, and a 502 occurs when a server acting as a gateway receives an invalid response from another server.
How do I fix a 500 Internal Server Error?
If you’re a visitor, start by refreshing the page, clearing your browser cache and cookies, or trying again after a few minutes, as the issue may be temporary. If you manage the website, review your server error logs, disable any recently installed plugins or software updates, verify your configuration files, and restart server or application services if necessary to identify and resolve the underlying problem.
What is the difference between a 4xx and a 5xx error?
A 4xx HTTP status code indicates a client-side error, meaning the request cannot be completed because of an issue with the browser or request itself, such as an incorrect URL, missing permissions, or invalid input. A 5xx HTTP status code indicates a server-side error, meaning the request was valid, but the website’s server encountered an internal problem that prevented it from fulfilling the request.
Can I fix an HTTP error code myself?
It depends on the type of error. If you’re a visitor, you can often resolve 4xx client-side errors by checking the URL for typos, refreshing the page, clearing your browser cache and cookies, or logging into the website if authentication is required. 5xx server-side errors usually stem from issues on the website’s server and typically require the site owner or hosting provider to resolve.
Do HTTP error codes affect SEO?
Yes, some HTTP error codes can affect a website’s search engine optimization (SEO). For example, excessive 404 Not Found errors can create a poor user experience if important pages are missing, while soft 404s may cause search engines to index low-value pages. Properly implementing 301 redirects for moved content and returning accurate 404 or 410 status codes for removed pages helps search engines crawl and index your website more effectively.