An unofficial blog that watches Google's attempts to move your operating system online since 2005. Not affiliated with Google.

Send your tips to

June 3, 2010

Decrypting the RLZ Parameter

If you install a Google software that lets you perform searches, you'll notice that Google search URLs include a new parameter called RLZ, which has a cryptic value. Google has open-sourced the RLZ library and we can now decrypt the value sent to Google every time you search.

"Client applications with the RLZ library can use explicit cohort tagging to manage promotion analysis. A client application with a particular tag can transmit that tag as it chooses for payments and analysis purposes. As an example, the RLZ parameter "rlz=1T4ABCD_enUS202" indicates the client application is Toolbar version 4, distributed with Abcd software bundle, English version, to a US user in December 2006. This empowers computation of metrics broken down into useful dimensions," explains Google.

"T4" is a codename for Google Toolbar 4 for Internet Explorer, but Google uses many other values: "C" for Google Chrome, "D" for Google Desktop, "B" for Google Toolbar for Firefox, "U" for Google Pack. "ADBR" is a code that identifies the distribution channel. "This correlates to how the user got the software (ie. they downloaded it by itself vs. it came pre-installed on their new computer vs. it came with a partner's software)." "c" is a value that tells Google if someone was already a Google user.

The library sends Google two other interesting values: install cohort (the country and week of the user's installation event) and first search cohort (the country and week of the user's first Google search). The week is measured as the number of weeks since Feb 3, 2003. For this example, "US239" informs Google that the user performed a search from the US in September 2007.

It's interesting to notice that Google measures the success of a campaign that promotes Google Toolbar, Google Chrome or other Google software by counting the number of Google searches.


  1. Wow!
    One more forward step ahead :)
    Google rocks as they do always :)

  2. In your example, "rlz=1T4ABCD_enUS202", is the "US202" the install cohort or the first search cohort? How are null values represented and what would the absence of a value indicate?

  3. @Anonymous:

    Usually, missing values are replaced with underscores. If there's no search cohort, the user hasn't performed a search using the software.

  4. I have RLZ values with missing fields and no underscores and was trying to figure out what is what... What would the following example indicate? rlz=1G1ACPW_FRFR357

  5. It does seem like the same syntax isn't used for every single search - I wonder what the difference is such as above when some of the values aren't there?

  6. Is there any rhyme or reason to the "Brand Code" cohort?


Note: Only a member of this blog may post a comment.