How Google Analytics Gets Information
When Google Analytics code gathers information about each pageview, how does it send that information back to the servers to process?
It sends it in the query string of a small file, called __utm.gif. In this way, a log file is created that contains all of the visit information for every single pageview, transaction and event. When the files are processed, Google Analytics can then string together individual events into a single visit.
Dissecting __utm.gif
A typical __utm.gif request is long and messy. Here is an example:
Although the URL looks overwhelming, it's pretty simple when broken down. First, there is the request for www.google-analytics.com/__utm.gif. This is the foundation of the Google Analytics reports. (If you are using Urchin, the __utm.gif will be requested from your own domain.)
There is a long query string with a dozen or so URL-encoded parameters, depending on when this is requested. Each parameter stores a specific piece of information that is used to populate the reports. Some parameters are only used in specific cases. Others must be there every time.
What Information Does Google Analytics Store?
The table below is directly from Google. It lists every piece of information that Google Analytics gathers for any given interaction with the website. We modified some descriptions.
Pageview Parameters
These parameters are included in the __utm.gif whenever a pageview is being reported.
| Variable | Description | Example Value |
|---|---|---|
| utmac* | Profile number. *Does not appear on Urchin hits. |
utmac=UA-2202604-2 |
| utmcc* | Cookie values. This request parameter sends all the cookies requested from the page. *In Urchin, this parameter is not used because the cookies are stored in the log files. |
utmcc=__utma%3D117243.1695285.22%3B%2B __utmz%3D117945243.1202416366.21.10. utmcsr%3Db%7C utmccn%3D(referral)%7C utmcmd%3Dreferral%7C utmcct%3D%252Fissue%3B%2B |
| utmcn | Starts a new campaign session. Either utmcn or utmcr is present on any given request. Changes the campaign tracking data; but does not start a new session. | utmcn=1 |
| utmcr | Indicates a repeat campaign visit. This is set when any subsequent clicks occur on the same link. Either utmcn or utmcr is present on any given request. | utmcr=1 |
| utmcs | Language encoding for the browser. Some browsers don't set this, in which case it is set to "-" | utmcs=ISO-8859-1 |
| utmdt | Page title, which is a URL-encoded string. | utmdt=analytics%20page%20test |
| utmfl | Flash Version | utmfl=9.0%20r48 |
| utmhn | Host Name, which is a URL-encoded string. | utmhn=x343.gmodules.com |
| utmje | Indicates if browser is Java-enabled. 1 is true. | utmje=1 |
| utmn | Unique ID generated for each GIF request to prevent caching of the GIF image. | utmn=1142651215 |
| utmp | Page request of the current page. | utmp=/testDirectory/myPage.html |
| utmr | Referral, complete URL. | utmr=http://www.example.com/aboutUs/index.php?var=selected |
| utmsc | Screen color depth | utmsc=24-bit |
| utmsr | Screen resolution | utmsr=2400x1920 |
| utmul | Browser language. | utmul=pt-br |
| utmwv | Tracking code version | utmwv=1 |
E-commerce Parameters
These parameters are only included in the __utm.gif when a transaction is being reported. One __utm.gif is requested for the transaction, and one additional __utm.gif is requested for each item in the transaction.
| Variable | Description | Example Value |
|---|---|---|
| utmt | A special type variable applied to events, transactions, items and user-defined variables. | utmt=Dog%20Owner |
| utmipc | Item variable: Product Code. This is the sku or product number. | utmipc=989898ajssi |
| utmipn | Item variable: Product Name, which is a URL-encoded string. | utmipn=tee%20shirt |
| utmipr | Item variable: Unit Price. Set at the item level. | utmipr=17100.32 |
| utmiqt | Item variable: Quantity | utmiqt=4 |
| utmiva | Item variable: Variations on an item or category. For example: large, medium, small, pink, white, black, green. String is URL-encoded. | utmiva=red; |
| utmtci | Transaction variable: Billing City | utmtci=San%20Diego |
| utmtco |
Transaction variable: Billing Country | utmtco=United%20Kingdom |
| utmtid | Transaction variable: Order ID, URL-encoded string. | utmtid=a2343898 |
| utmtrg | Transaction variable: Billing region, URL-encoded string. | utmtrg=New%20Brunswick |
| utmtsp | Transaction variable: Shipping cost. | utmtsp=23.95 |
| utmtst | Transaction variable: Affiliation. Typically used for brick and mortar applications in ecommerce. | utmtst=google%20mtv%20store |
| utmtto | Transaction variable: Grand total. | utmtto=334.56 |
| utmttx | Transaction variable: Tax. Values as for unit and price. | utmttx=29.16 |
Special Parameters
These parameters are only used in special circumstances, like event tracking.
| Variable | Description | Example Value |
|---|---|---|
| utme | Event Tracking Data Parameter | Value is encoded. |
| utmt | A special type variable applied to events, transactions, items and user-defined variables. | utmt=Dog%20Owner |
