Status Response Codes

Find status response codes by submitting a relevant keyword or status code.

Instructions

• This tool allows you to search for status response codes even if these are not part of IANA's Status Code Registry (IANA, 2015; Wikipedia, 2015).
• To use the tool, just submit a keyword or valid status code from 100 to 599.
• The tool is case-insensitive, so you can use lower or upper cases.

What is computed?

• Unlike similar tools which only match status codes, ours also match keywords.
• For instance, submitting [404], [Not Found], [Not], or [Found] returns the same record.
• If other records partially match your query, these are also returned.

A status code of 0?

• Some AJAX scripts return an http status code of 0. How could this be possible?
• A status code of 0 is not a true header response code, but the evaluation of an unsuccessful response code as a falsey value. Said evaluation is done according to a particular programming language or browser/API library. For instance, client-side (400+) or server-side (500+) status codes are classified as errors and as such can be restated as 0, a falsey value.

  To illustrate, an AJAX request for an unregistered domain name should return a falsey value of 0 because no server and IP are associated to it.

  Furthermore, an AJAX request for a registered domain name whose host has been removed from the Web should also return a status code of 0. The latter was observed during the Heartbleed outbreak days.

What is a falsey value?

• A falsey value is something that evaluates to false according to specific programming rules (Phabricator, 2015; PHP.net, 2015a, 2015b, 2015c). For instance, in almost all programming languages 0 is a falsey value.
• As shown in the following comparative, each programming language has its own way of classifying falsey values.
  JavaScript

  • false (case-sensitive)
  • null (case-sensitive)
  • empty strings (in double or single quotes)
  • 0 (as a number)
  • undefined (case-sensitive)
  • NaN (case-sensitive)

  PHP (version 5)

  • false (case-insensitive)
  • null (case-insensitive)
  • empty string (in double or single quotes)
  • 0 (as a number or string)
  • 0.0 (as a float)
  • empty arrays
  • SimpleXML objects created from empty tags
  Notice that false and null written in lower cases evaluates to false in JavaScript, while written in lower or upper cases evaluates to false in PHP. Note also that 0 written as a number evaluates to false in JavaScript, while written as a number or string evaluates to false in PHP.
• Furthermore, some programming languages have native functions that are shortcuts for a combination of falsey values. For instance, in PHP

  isset() is a shortcut for

  if(($var)&&(!$var==NULL))

  while empty() is a shortcut for

  if((!isset($var))||($var==false))

Who can use this tool?

• Webmasters, developers, and programmers.

References

• IANA (2015). Hypertext Transfer Protocol (HTTP) Status Code Registry.
• Phabricator (2015). PHP Pitfalls.
• PHP.Net (2015a). Boolean Types.
• PHP.Net (2015b). PHP isset() function.
• PHP.Net (2015c). PHP empty() function.
• Wikipedia (2015). List of HTTP Status Codes.

Feedback

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