Errors and Server HTTP Response Header Codes

Complete list of server HTTP response codes and related errors technical SEO program can recognize.

HTTP Response Codes Server Can Send in HTTP Headers

You can view the HTTP response and program codes for URLs after the website scan has finished:

For a full list of possible codes and their explanations, see the table below:

Code Description More Info
HTTP Response Codes
100 Continue
101 Switching Protocols
200 OK
201 Created
202 Accepted
203 Non-Authoritative Information
204 No Content
205 Reset Content
206 Partial Content
300 Multiple Choices
301 Moved Permanently The URL redirects to another. To find out where you linked/used/etc. this URL, see internal linking.
302 Moved Temporarily (Found)
303 See Other
304 Not Modified
305 Use Proxy
306 Switch Proxy
307 Temporary Redirect
400 Bad Request See rcTimeoutConnect: Timeout: Generic for possible cause and solution.
401 Unauthorized Website may require login or similar.
402 Payment Required
403 Forbidden See rcTimeoutConnect: Timeout: Generic for possible cause and solution.
Possibly a server module denying unknown crawlers access. See help on problematic websites.
404 Not Found The URL does not exist. To find out where you linked/used/etc. this URL, see internal linking.
405 Method Not Allowed
406 Not Acceptable
407 Proxy Authentication Required
408 Request Timeout
409 Conflict
410 Gone
411 Length Required
412 Precondition Failed
413 Request Entity Too Large
414 Request-URI Too Long
415 Unsupported Media Type
416 Requested Range Not Satisfiable
417 Expectation Failed
500 Internal Server Error See rcTimeoutConnect: Timeout: Generic for possible cause and solution.
503 Service Temporarily Unavailable See rcTimeoutConnect: Timeout: Generic for possible cause and solution.
504 Gateway Timeout
505 HTTP Version Not Supported
TechSEO360 Response Codes
0 rcVirtualItem: Virtual Item No request has been done by the crawler for this URL.

Happens in cases where a directory example/ is not used, linked or redirected from anywhere (and thus with default settings not crawled), but has URLs underneath that are, e.g. example/file.html.

If there are no URLs underneath like described above - rcVirtualItem URLs will not appear in Analyze website data.

Alternatively, you can force the crawler to handle such URLs by checking option: Scan website | Crawler options | Always scan directories that contain linked URLs.

For more details, see the internal linking help page.
-1 rcNoRequest: No Request No request has been done by the crawler for this URL.

You will usually only see this under the following conditions:
  1. The URL is excluded in both analysis filters and output filters or alternatively disallowed by robots.txt .
  2. You have unchecked:
    • Older versions:
      • Scan website | Crawler options | Apply "webmaster" and "output" filters after website scan stops
    • Newer versions:
      • Scan website | Output filters | After website scan stops: Remove URLs excluded
      • Scan website | Webmaster filters | After website scan stops: Remove URLs with noindex/disallow
-2 rcUnknownResult: Unknown Result Server responded with an unrecognized response code.
-3 rcTimeoutGeneric: Timeout: Generic Possible solutions if you have overloaded your server:
  • Lower amount of simultaneous connections.
  • Increase timeout values. Increase connection retries.
  • Resume scan. Crawler will attempt connect again.
-4 rcCommError: Communication Error Possible reasons:
  • Webserver did not obey HTTP or HTTPS protocol.
  • The server/domain of the URL did not exist.
  • Firewall or similar is blocking connections.
-5 rcTimeoutConnect: Timeout: Connect See rcTimeoutConnect: Timeout: Generic
-6 rcTimeoutRead: Timeout: Read See rcTimeoutConnect: Timeout: Generic
-7 rcCommErrorDecompress: Communication Error: Decompress
-8 rcRedirectCanonical: Redirect: Canonical Canonical URLs
-9 rcRedirectIndexFileDirRoot: Redirect: Index File Directory Root Duplicate URLs
-10 rcCommErrorSocket: Communication Error: Sockets Possible reasons:
  • The server/domain of the URL did not exist. Could be a problem with DNS.
-11 rcMetaRefreshRedirect: Meta Refresh Redirect Duplicate URLs
-12 rcCommErrorChunkedWrong: Communication Error: Chunked Wrong
-13 rcAjaxSnapshotRedirect: Redirect: Ajax Snapshot Redirect Google proposed AJAX snapshot solution where example.com/ajax.html#!key=value corresponds to example.com/ajax.html?_escaped_fragment_=key=value

AJAX is a Javascript/browser technology that allows Javascript to communicate directly with a server through HTTP. This allows JS to update the browser content without any page reloads.
-14 rcRedirectNoSlashDirRoot: Redirect: No Slash Directory Root Duplicate URLs

The usage of some of the program specific codes is controlled by the option: Scan website | Crawler options | Use special "response" codes for when page URLs use canonical or similar.

This option is unchecked by default for new projects in TechSEO360 since this software shows extended information in the data columns URL Flags and Crawler Flags which can be used in conjunction with SEO reports and other data columns.

Graphics in Website Analysis

After a website scan has finished, you can see all URLs found in the analyze website tab.

You can see the state of the URLs by their icons:
  • ok : Server response 200 - OK.
  • error : Server error response code, e.g. 404 - Not Found.
  • unknown : Server HTTP response code never checked or unknown.

For details about an URL, just view the R.Code (response code) column value.

Handling Soft 404 Errors

The term Soft 404 errors is a situation where a website should return response code 404 : Not Found for an URL, but instead returns 200 : Found.

Incase you have such URLs, and you do not want them in your generated sitemaps, you can use the custom search feature to search for the text and code specific to pages showing a soft error. After scan, just remove the unwanted URLs before generating the sitemap files.

Solutions to Various Types of Server and Crawler Errors

When scanning a complete website, some URLs may result in a standard HTTP error response code, and other URLs may simply error in different manner, e.g. through connect or read timeouts.

Some common examples are:
  • 500 : Internal Server Error, 503 : Service Temporarily Unavailable and -4 : CommError:
    These are reported when a complete connection failure happens. These can e.g. be caused by firewall issues.
  • 404 : Not Found:
    To solve broken links, read the help page about internal linking.

To solve more kinds of issues including server error HTTP response codes see:
TechSEO360 | help | previous | next
SEO website crawler tool that can find broken links, analyze internal link juice flow, show duplicate titles, perform custom code/text search and much more.
This help page is maintained by
As one of the lead developers, his hands have touched most of the code in the software from Microsys. If you email any questions, chances are that he will be the one answering.
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