What is Google Analytics' __utm.gif used for?

Question

What is Google Analytics' __utm.gif used for (You know that 1px × 1px gif image that loads on every page with Google Analytics)?

I see my screen resolution and other stuff in the URL. Is that how they send all the site's data back to their servers? With a get request on an image? Cause that's kinda uber clever!

Answer 1

it is a web beacon. Read this: https://en.wikipedia.org/wiki/Web_beacon

Answer 2

The image is dynamically generated and the URL is linked to your account.

When you request the image, Google knows your IP address and some other basic info and can deduce your location, the time of the request, your browser, etc.

The main reason, though, is cross-site-scripting. Requesting an image is easier and completely cross-browser, as you'd have to use JSON to send a request with that information back to Google.

Answer 3

Is that how they send all the site's data back to their servers?

Yes.

Answer 4

Yes, you are correct. This request is used to send Google details about a particular page request, namely:

• URL pageview information
• Campaign information
• Ecommerce data
• Browser properties
• Visitor IDs