Tagging or Logfile-Analysis?

There are two common measurement methods that are used for Web Analytics.

  • Measurement on the client side (tagging)
  • Measurement on the server side (log file analysis)

Let’s have a look at how a page is processed on the web:

  1. A user selects a URL by typing it in, clicking a link or a choosing bookmark.
  2. The client (browser) sends a request to this URL on the internet and waits for response
  3. The client receives a response from a server
  4. The browser loads for more required data over the Internet
  5. The browser renders the page.

We should assume that the client receives exactly the data that the server sends. That is why an analysis of server log files should be as precise as a measurement at the client. But this is not the case as we will show.

The internet is not a cable connecting directly one server to a client. It is a conglomerate of many different network components and servers. Each of those components could interfere or manipulate a request by a client or the response of a server. Each request passes many hops before it reaches a server. The same is true for the responses.

the internet is not a cable but a network

Thus there is no such thing as a truth that you everybody agrees on. You might see the same thing from multiple angles and maybe come to different conclusions.
A server does not only serve human ‚visitors‘, but also many programs requesting files. (crawlers) These hits also show up in the server’s log file but users behind a proxy are (mostly) invisible to the server.

The measurement close to the client is usually done with tagging method. This means that the user’s Browser sends a request to a tracking server via JavaScript. Because the request is issued via JavaScript robots and spiders are (usually) irrelevant for this measurement method. Users or browsers can be distinguished by using cookies as opposed to their IP address, thus even users behind proxies can be distinguished sufficiently well.

Pro log file analysis:

  • Everything that relates to the webserver can be determined really well.
  • No changes to the website necessary
  • You don’t need to have a tracking server

Pro tagging method:

  • Everything that affects the user can be measured really well.
  • You can collect more data e.g. revenues, orders, shopping carts, …
  • Tagging allows you to gather data from multiple websites or domains running on different servers
  • The measurement runs on the client and thus doesn’t put additional load on your webserver
  • gathers data from behind proxies

Which of the methods should I choose? -> Both methods!

For administrators who want to know which files are requested (and how often), when the Google Bot hits your systems and sets them under load and which error pages are displayed the log file analysis is very helpful.

For online marketing, e-commerce and other business relevant questions, where the users or customers and their behavior is relevant, tagging is the method of choice.

If you are interested in users, then you measure close to the user (tagging method)
If you are interested in the server, then you measure near the server (logfile analysis)