HTTP Header Sniffer

GigaBook Web Developer Tools

Types of response codes

Response codes fall under five categories:

  • 1xx Informational
  • 2xx Success
  • 3xx Redirections
  • 4xx Client Error
  • 5xx Server Error

Some of the most common you're likely to encounter within these categories are:

  • 200 - OK
  • 301 - Moved Permanently
  • 400 - Bad Request
  • 401 - Unauthorized
  • 404 - Not Found
  • 500 - Internal Server Error
  • 502 - Bad Gateway
  • 503 - Service Unavailable

A full list of available response codes can be found in the W3 protocols.

Testing User Agents

Within the tool we've provided a list of common user agents so you can view how http responses may vary. Detecting user agents allows sites to tailor their response depending on the browser or device that is making the request. So for example, a site might detect the following user agent:


This tells the site that the user is browsing on an iPhone.

Uses of detecting user agents

  • Serve simpler web pages for old browser compatability
  • Customising content for different devices (e.g. lightweight mobile version)
  • Statistics - google analytics uses this to provide a break down of how users are viewing your site
  • Blocking site crawlers

Tool Features

  • Check http or https web site header responses.
  • Set the user agent to see how the site responds differently.

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