Meaning of Parameters in a Google Query

A typical Google search URL from Firefox might look like this:

http://www.google.com/search?q=tools&ie=utf-8&oe=utf-8
&rls=org.mozilla:en-US:official&hl=en-US&client=firefox-a

Although this is a very simple search, Google adds a lot of parameters (marked with bold) to identify the source of the query, the language of the interface and the encodings. You'll obtain the same results if you type:
http://www.google.com/search?q=tools

Let's see some of the most common parameters in a Google query:

Languages

ie = encoding of the input (default: utf-8)
oe = encoding of the output, the results (default: utf-8)
hl = language of the interface (default:en, you can try xx-bork or xx-hacker)
lr= language of results (default:en)

Source

sourceid = type of the source (ie7, opera, navclient, navclient-ff - navclient is used for Google software like the toolbar)
client = similar to sourceid (safari, firefox-a)
rls = version of the client, the language (example: rls=GGLD,GGLD:2003-35,GGLD:en for Google Desktop)

Results

q, as_q= query, what you type in the search box
start=number of the first result from the page (starts from 0)
num=number of results in a page
filter= 0 or 1 (hide duplicate results)

Advanced search

as_epq=exact phrase (instead of typing quotes in the query, you can use this parameter)
as_filetype= file format (example:as_filetype=pdf)
as_ft=include / exclude a file format defined with as_filetype (values: i, e)
as_qdr=date of the results (values: m3, m6, y - last 3 or 6 months, a year)
as_nlo= find numbers greater than
as_nhi= find numbers lower than (example: as_nlo=7&as_nhi=9 to search integers from 7 to 9 - alternatively, you could type 7..9 in the query)
as_occt=where can appear the words in the page (some values: any, body, url, title)
as_sitesearch= restrict to a site (example: as_sitesearch=cnn.com)
as_dt=include / exclude a domain (values: i, e)
as_rights= type of the license (for Creative Commons licenses)
safe= safe search (values: active, off)

Using these parameters you can understand better a Google query URL from your site stats and can create an advanced query without using Advanced Search dialog:

http://www.google.com/search?as_epq=matrix+1..3&num=25&hl=en&as_qdr=m3

searches for "matrix 1", or "matrix 2" or "matrix 3" in the sites updated in the past 3 months and returns 25 results.

{ Idea by Corsin Camichel. }