The Complete Guide to HTTP Status Codes and Their Impact on SEO

HTTP status codes play a critical role in web performance and SEO. It’s essential for site owners and SEO professionals to understand the differences between these codes and their implications for a website. Since HTTP status codes apply to both HTTP and HTTPS protocols, having a comprehensive understanding of them is invaluable. In this article, we’ll explore each group of HTTP status codes, discuss their meanings, and explain how to identify and resolve potential issues before they escalate.

1XX codes – Informational responses

HTTP response codes from 100-199 are informational, indicating that the server has received the request and is processing it. Though rare, these codes are useful for webmasters and SEO specialists to understand as they can aid in diagnosing and fixing issues.

100 Continue

This code means that the initial part of a request has been received and the client can continue the request. The response proves especially useful for large file uploads, as it ensures that the client sends the full body only after the initial headers are accepted. This helps to limit unnecessary data transfer.

101 Switching Protocols

This code is the server’s acknowledgment of an Upgrade request header sent by the client, signaling that it is switching to the specified protocol. A common example is the transition from HTTP/1.1 to HTTP/2, which enhances performance by reducing latency and improving data transfer efficiency.

102 Processing

This status indicates that the server has received the request and is working on it but does not yet have a final response. It helps prevent timeouts in cases where processing the request requires significant time, ensuring the client remains informed of the ongoing process.

103 Early Hints

Early Hints status codes enable the server to send preliminary response headers before the full HTTP response is ready. This approach allows clients to begin preloading resources, which can significantly improve web page load times. By starting the resource loading process earlier, websites can deliver a faster and more seamless user experience.

2XX codes – Successful responses

HTTP status codes in the 200–299 range indicate successful requests. These codes confirm that the server received, understood, and processed the request successfully — the ideal outcome for most HTTP interactions. When your site returns 2XX status codes, it signals to search engines that your website is reliable and well-maintained, which can positively influence your rankings.

200 OK

This is the default HTTP response for successful, non-error pages. For SEO, a 200 status code ensures that the page can be crawled and indexed without issues. Regularly checking for 200 status codes helps maintain content accessibility, prevent ranking declines, and avoid potential site errors.

201 Created

201 responses indicate that a resource has been successfully created as a result of the request. Commonly seen in RESTful APIs, this status is returned when a new resource is added to a database, signaling that the action was successfully completed.

202 Accepted

This code means the request has been accepted for processing but is not yet complete. It is particularly useful for asynchronous operations, where the server queues the action and informs the client that the process is underway.

203 Non-Authoritative Information

The server successfully completed the request but is providing information that originated from a source other than the server itself. Often used by proxy servers, it informs clients that the data may have alternative origins.

204 No Content

204 indicates that the request was successful, but there is no content to return in the response body. This status is typical for operations where the server updates a resource without altering the displayed content.

205 Reset Content

The server has successfully processed the request and informs the client to reset the document that initiated the request. This status is commonly used after form submissions to prompt the client to clear the input fields for a fresh start.

206 Partial Content

When a client requests only a specific part of a resource, the server responds with this code and delivers the requested portion. This status is particularly useful for resuming interrupted downloads or fetching segments of large files.

207 Multi-Status

A single request can trigger multiple operations, and this status communicates the results of each operation. It is commonly used in WebDAV applications to summarize the outcomes of different actions in one response.

208 Already Reported

This code tells the client that the members of a WebDAV binding have already been listed in a previous response. As a result, there is no need to enumerate them again in subsequent responses.

226 IM Used

The server satisfies a GET request by returning a resource encoded with delta updates, which represent the changes made since a previous version. This status is designed to optimize incremental updates and reduce redundant data transfers.

3XX codes – Redirection messages

HTTP status codes in the 300–399 range represent redirection messages. These codes indicate that additional action is needed from the client to complete the request. Redirects are a critical aspect of SEO and website management, as they help ensure users and search engines are directed to the correct content. Proper handling of 3XX codes is essential to avoid losing link equity, frustrating users, or negatively impacting search rankings.

300 Multiple Choices

This status code presents multiple options for the requested resource, allowing the client to choose from them. It is often used in authentication scenarios to inform the client of alternative content or access points.

301 Moved Permanently

One of the most important codes for SEO, this status directs both users and search engines to a new URL permanently. A properly implemented 301 redirect transfers link equity to the new URL, helping preserve search rankings and organic traffic.

302 Found

This code notifies the client that the requested resource is temporarily located at a different URL. While it allows temporary redirection, it does not pass SEO value like a 301 redirect, making it unsuitable for permanent changes.

303 See Other

The client is redirected to a different URI using the GET method, regardless of the original request method. This ensures that all HTTP methods are idempotent, meaning they can be safely repeated, which improves consistency and reliability in HTTP operations.

304 Not Modified

This status tells the client that the requested resource has not changed since the version specified in the request headers. It speeds up content delivery by avoiding unnecessary data transfers and allowing the client to use a cached version.

305 Use Proxy

The client is instructed to access the requested resource through a proxy specified in the Location header. This status code identifies an alternative access point or pathway for retrieving the resource.

307 Temporary Redirect

This code functions similarly to a 302 but ensures that the request method and body remain unchanged when the client follows the redirection. It is useful for maintaining consistency during temporary relocations.

308 Permanent Redirect

Similar to a 301 redirect, this code indicates a permanent change to the resource’s location. However, unlike 301, the method and body of the original request remain unaltered when the redirection is followed, ensuring that the original request details are preserved.

4XX codes – Client error responses

HTTP status codes in the 4XX range indicate errors caused by the client. These errors occur when the server is unable to process a request due to issues such as a missing resource (e.g., 404) or insufficient permissions (e.g., 403). Managing these error codes is essential for maintaining both website usability and SEO performance. When users encounter these errors, they are likely to leave your site, potentially harming your search rankings if the issues are not resolved quickly.

400 Bad Request

The server cannot process the request due to invalid syntax, such as malformed requests or missing parameters. Ensuring that requests are properly formatted allows for clear communication between the client and the server.

401 Unauthorized

Access to the requested resource is denied because the request lacks valid authentication credentials. Users must provide proper authentication to gain access, ensuring secure and controlled entry to protected areas.

403 Forbidden

Although the server understands the request, it refuses to authorize it. This often happens when a user does not have sufficient permissions to access a resource. Proper configuration of access controls can prevent this error.

404 Not Found

A 404 error indicates that the resource is unavailable on the server. This can result from broken links, deleted pages, or incorrect URLs. Regular audits and updates to internal and external links help maintain usability and SEO performance.

405 Method Not Allowed

When a request uses an HTTP method unsupported by the server for the targeted resource, this error occurs. Aligning request methods with server-supported operations resolves the issue.

406 Not Acceptable

This code means the server is unable to generate a response matching the criteria set in the client’s request headers. Adjusting the headers or expanding the server’s capabilities to handle varied formats can fix this error.

407 Proxy Authentication Required

Before accessing the resource, the client must authenticate itself with a proxy. This additional layer of authentication secures intermediary access points and prevents unauthorized usage.

408 Request Timeout

The request took too long to reach the server, causing the connection to time out. To address this, optimizing server timeout settings and reducing latency in client requests is essential.

409 Conflict

A conflict arises when the request cannot be completed due to a contradiction with the current state of the resource. These errors often stem from concurrent modifications and require careful handling to resolve.

410 Gone

This status informs that the requested resource has been permanently removed and is no longer available. Communicating resource removals to search engines via proper redirects or status codes helps maintain SEO integrity.

411 Length Required

A request will be rejected if it does not include the Content-Length header. To ensure successful processing, the client must specify and validate the length of the request.

412 Precondition Failed

This status occurs when a request does not meet one or more of the preconditions defined in its headers. Ensuring that requests comply with specified preconditions resolves this issue.

413 Payload Too Large

The server cannot process a request because the payload size exceeds its limits. Reducing the size of the payload or optimizing request formats addresses this error.

414 URI Too Long

Excessively long URIs, often due to too many query parameters, can overwhelm the server. Shortening URIs improves processing efficiency and avoids this issue.

415 Unsupported Media Type

When the server cannot process the media format of the request, this error is returned. Ensuring that media formats are compatible with server capabilities resolves the problem.

416 Range Not Satisfiable

This status indicates that the range specified in the Range header is invalid. Adjusting the range to align with the resource’s bounds resolves the error.

417 Expectation Failed

The server cannot meet the requirements specified in the Expect header of the request. Reviewing and modifying the expectations ensures compatibility with the server.

418 I’m a Teapot

This humorous status code, created as an April Fools’ joke in 1998, signifies that the server is a teapot and cannot brew coffee. While it has no practical use, it remains a fun part of HTTP lore.

422 Unprocessable Entity

Semantic errors prevent the server from processing a well-formed request. Resolving these issues requires reviewing and correcting the request’s logic.

423 Locked

The requested resource is locked and cannot be modified. This code is commonly used in WebDAV, and understanding locking mechanisms helps prevent conflicts.

424 Failed Dependency

This error occurs when the success of one request depends on a prior request that failed. Resolving the initial issue allows the dependent request to succeed.

425 Too Early

A server may reject a request if it suspects it could be replayed. Proper timing mechanisms and validation processes can address this concern.

426 Upgrade Required

The server requires the client to upgrade to a specific protocol, such as HTTP/2, for compatibility. Following the server’s recommendation ensures improved performance and compatibility.

428 Precondition Required

This status requires the request to meet specific conditions to prevent issues like lost updates. Implementing conditional requests ensures consistency and resource integrity.

429 Too Many Requests

When a client exceeds the allowed request rate, this error is triggered. Implementing rate-limiting controls helps manage request volumes effectively.

431 Request Header Fields Too Large

The server refuses to process a request with excessively large headers. Reducing header size or making them more concise resolves this issue.

451 Unavailable For Legal Reasons

Access to the requested resource is restricted due to legal or regulatory prohibitions. Ensuring compliance with legal requirements is essential for ethical and lawful operations.

5XX codes – Server error responses 

HTTP status codes in the 5XX range indicate server-side errors that prevent the server from fulfilling a request. These errors are critical for user experience and search engine optimization, as they can disrupt website functionality. Understanding these codes and addressing the underlying issues ensures a healthier and more reliable website.

500 Internal Server Error

This generic error occurs when the server encounters an unexpected condition that prevents it from fulfilling the request. Analyzing server logs and conducting root cause investigations are common ways to identify and resolve these issues.

501 Not Implemented

Because the server does not support the functionality of the request, this cannot be fulfilled. To enable the server to support different functionalities of requests, the server capabilities must be updated. 

502 Bad Gateway

This error indicates that a server acting as a gateway or proxy received an invalid response from an upstream server. Coordinating between proxy servers and upstream services ensures smoother communication and prevents this error.

503 Service Unavailable

A 503 status means the server is temporarily unable to handle the request, often due to overload or maintenance. Implementing load balancers and monitoring systems can reroute traffic and prevent downtime.

504 Gateway Timeout

This status occurs when a server acting as a proxy cannot get a timely response from an upstream server. Optimizing server response times and improving upstream queries helps avoid this issue.

505 HTTP Version Not Supported

The server does not support the HTTP protocol version used in the request, as it checks for protocol compatibility.

506 Variant Also Negotiates

A circular reference in transparent content negotiation results in this error. Fixing recursive configurations resolves the issue and ensures proper content delivery.

507 Insufficient Storage

The server cannot fulfill the request due to insufficient storage space. Allocating additional server resources and monitoring storage usage reduces the likelihood of this error.

508 Loop Detected

This status is triggered when the server detects an infinite loop while processing a request with Depth: infinity. Correcting recursive calls and resource configurations prevents this error.

510 Not Extended

The server requires additional request parameters to fulfill the request. Adding the necessary extensions or headers ensures the server can process and return a valid response.

511 Network Authentication Required

Access to the network is denied until the client authenticates itself, commonly seen in Wi-Fi captive portals. Implementing proper authentication mechanisms ensures controlled access to the network.

HTTP status codes and their effect on SEO

Understanding how HTTP status codes influence SEO is essential for maintaining an accessible, optimized website for both search engines and users. Each status code carries unique implications for SEO performance. Here’s a breakdown of key codes and their impact:

200 OK

A successful response indicates that the requested content is accessible to both users and search engines without issues. Regularly monitoring your site using tools like Google Search Console helps identify and resolve problems early, ensuring that most pages return a 200 status.

301 Moved Permanently

This code signifies a permanent redirect from one URL to another, transferring link equity to the new page. Proper implementation of 301 redirects during URL restructuring or domain migrations ensures SEO value is preserved and can even enhance rankings.

302 Found

Temporary redirects guide users to an alternate URL for a limited time. While useful for short-term changes like promotional pages, overuse can confuse search engines about the preferred URL. Use 302 redirects sparingly to avoid potential SEO complications.

304 Not Modified

Returning a 304 status informs the client that the content hasn’t changed since the last request, conserving server resources and “crawl budget.” Configuring cache control and HTTP headers properly allows you to reap the benefits of this status by optimizing server performance without compromising the user experience.

404 Not Found

When a requested resource cannot be located on the server, a 404 error is returned. Excessive 404 errors can harm SEO by signaling poor site maintenance. Creating custom 404 pages with helpful navigation options improves user experience while minimizing negative SEO effects.

410 Gone

Using a 410 status permanently indicates to search engines that a resource has been intentionally removed. This prevents search engines from wasting crawl efforts on the page. However, ensure alternative resources or updated content are available to retain user engagement and maintain SEO health.

500 Internal Server Error

These critical errors prevent crawlers from accessing your site and can severely damage SEO. Immediate resolution is essential. Automated alert systems for 500 errors enable rapid response by site administrators, minimizing downtime and preserving SEO performance.

503 Service Unavailable

A temporary error indicates the server is overloaded or undergoing maintenance. Extended outages may suggest deeper issues that threaten site stability and SEO. Optimizing server capacity and implementing failover mechanisms can ensure service continuity and stable SEO outcomes.

Monitor and fix response code issues regularly

Diagnosing and resolving HTTP status code issues is essential for maintaining good site management and top-tier SEO performance. Regular monitoring ensures that your site remains healthy, accessible, and optimized for both users and search engines. Dedicated tools make this process more manageable:

Google Search Console

Google Search Console is a free and powerful tool for monitoring the performance and health of your website. Follow these steps to use it effectively:

1. Log in to Google Search Console and navigate to the “Coverage” report.
2. Review errors under the categories “Error,” “Valid with warnings,” or “Excluded.”
3. Click on each error type to see descriptions of the affected URLs and the associated status codes.
4. Resolve the issues by fixing server configurations, redirecting problematic URLs, or correcting content errors.
5. After resolving the issues, mark them as fixed. This prompts Google to re-crawl or re-index the pages to confirm the corrections.

Similarweb Site Audit Tool

The Site Audit Tool from Similarweb provides detailed insights and actionable advice for addressing HTTP status code issues. Here’s how to use it:

1. Sign in to Similarweb and create a new project for your website.
2. Run a full site audit to identify technical SEO issues, including 4XX and 5XX errors.
3. Review the audit report, which organizes issues by severity and offers clear recommendations for fixes.
4. Address high-severity issues first to ensure quick recovery and improved ROI for your SEO efforts.
5. Schedule regular audits to proactively detect and resolve problems before they escalate.

Maintain a healthy and high-performing website

Consistently monitoring and resolving HTTP status code issues is key to building a fast, reliable, and well-performing site. Tools like Google Search Console and the Similarweb Site Audit Tool empower you to stay on top of your site’s core health. By addressing issues promptly, you’ll set your site up for sustained SEO success and an improved user experience.

FAQs

Can HTTP status codes affect site speed?

Yes, certain status codes, such as 503 and 504, can be associated with server overload or network issues, potentially slowing down your site. Ensuring efficient communication between servers and maintaining sufficient server capacity helps optimize load times and, in turn, supports SEO health.

How do 5XX codes affect SEO?

5XX errors indicate server-side issues that prevent search engines from crawling your site. These errors can reduce the frequency of crawling and indexing, which negatively impacts SEO. Addressing these errors promptly is critical to maintaining site visibility and performance.

What is the difference between 301 and 302 redirects?

A 301 redirect indicates a permanent move and passes SEO value, such as link equity, to the new URL. A 302 redirect is temporary and does not transfer SEO value, which can harm rankings if used incorrectly for long-term changes.

How do 404 errors impact SEO?

404 errors occur when a requested page cannot be found, leading to a poor user experience and potentially devaluing backlinks. Too many 404s can negatively affect SEO. To mitigate this, fix broken links or redirect them to relevant pages.

Why do I need to monitor HTTP status codes regularly?

Regular monitoring helps detect and resolve HTTP status code issues before they impact user experience or search rankings. Tools like Similarweb’s Site Audit Tool provide actionable insights, enabling you to address problems efficiently and maintain your site’s health.