HTTP Browser Header Checker

About the Author: Lammert Bies is a dad, husband and polyglot. He is developing embedded systems since the eighties. Used machine learning before it had a name. Specializes in interconnecting computers, robots and humans. Was a Google Mapmaker Advocate and speaker on several international Google conferences from 2011 until the plug was pulled on Mapmaker in 2017. Bughunter with Google. Currently spreading artificial intelligence to the wildest locations in production environments. He never stops learning.

• Introduction to HTTP browser headers
• Your HTTP browser headers
• Most common HTTP browser headers

Introduction to HTTP browser headers

When making HTTP requests for pages over the Internet, a browser sends a number of information header lines to the web server which will serve that request. Those HTTP information headers do not only contain information about the page that has to be retrieved, but also contain configuration and system information of the browser and of the computer the browser is running on. This information can be used by the web server to serve the best matching content to the client.

Most Internet users—and also many website builders—are not aware of this extra set of information which accompanies every request. Proper use of these HTTP headers by web servers can however improve the user experience significantly by matching the response as close as possible to the user and browser preferences. One example is serving web pages in the primary language of the browser. Another example is serving light weight pages when a mobile device is connecting, or send images in the format best processed by that particular
browser or output device.

Your HTTP browser headers

Most common HTTP browser headers

Browsers send a variety of HTTP headers. This list contains the most common HTTP headers you will see coming from regular browsers and bots like the crawlers from the major search engines.

Accept

This HTTP header contains the MIME types which are accepted by the browser. This can be a list of specific MIME types, but the list may also contains wildcards. The entries in the list are separated by commas. Priority values can be assigned to each MIME type by adding a semicolon followed by a q=val parameter. The priority value val ranges from 0.0 to 1.0 where higher values represent higher priority. In this way the browser can request specific content types, for example JPG files over PNG files if both are available on the server.

Example: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8

Accept-language

The browser sends preferred language information in this HTTP header. The content of the HTTP header is a list of one or more languages. Each language is represented by a two character code like en for English, or a five character code like en-US for American English if a subset of a specific language is requested. Entries in the list are separated by commas. A priority value can be assigned with each language by adding a semicolon followed by a q=val setting. The priority value val may range from 0.0 to 1.0, where 1.0 is the highest priority and 0.0 the lowest.

Example: en,en-us;q=0.7,nl;q=0.3