Web Analytics Technologies, Back to basic series

The Second in the Web Analytics Back to basic series, is all about web analytics technologies.

Web analytics technologies

There are two main technological approaches to collecting web analytics data. The first method, logfile analysis, reads the logfiles in which the web server records all its transactions. The second method, page tagging, uses JavaScript on each page to notify a third-party server when a page is rendered by a web browser.

Web server logfile analysis: Web servers have always recorded all their transactions in a logfile.
*A server log is a file (or several files) automatically created and maintained by a server of activity performed by it.

Page Tagging (Web beacon technology): Code on each tracked page references a javascript file. The javascript file sends data about the page and the user’s machine back to host servers, along with an image request. Host servers send back an invisible 1x1 pixel image, and record the data sent by the javascript file.
The web analytics service also manages the process of assigning a cookie to the user, which can uniquely identify them during their visit and in subsequent visits.

With the increasingly popularity of Ajax-based solutions, an alternative to the use of an invisible image, is to implement a call back to the server from the rendered page. In this case, when the page is rendered on the web browser, a piece of Ajax code would call back to the server and pass information about the client that can then be aggregated by a web analytics company.

Logfile analysis vs page tagging

Both logfile analysis programs and page tagging solutions are readily available to companies that wish to perform web analytics. In many cases, the same web analytics company will offer both approaches. The question then arises of which method a company should choose. There are advantages and disadvantages to each approach.

Advantages of logfile analysis

The main advantages of logfile analysis over page tagging are as follows.

• The web server normally already produces logfiles, so the raw data is already available. To collect data via page tagging requires changes to the website.
• The web server reliably records every transaction it makes. Page tagging relies on the visitors' browsers co-operating, which a certain proportion may not do (for example, if JavaScript is disabled).
• The data is on the company's own servers, and is in a standard, rather than a proprietary, format. This makes it easy for a company to switch programs later, use several different programs, and analyze historical data with a new program. Page tagging solutions involve vendor lock-in.
• Logfiles contain information on visits from search engine spiders. Although these should not be reported as part of the human activity, it is important data for performing search engine optimization.
• Logfiles contain information on failed requests; page tagging only records an event if the page is successfully viewed.

Advantages of page tagging

• The main advantages of page tagging over logfile analysis are as follows.
• The JavaScript is automatically run every time the page is loaded. Thus there are fewer worries about caching.
• It is easier to add additional information to the JavaScript, which can then be collected by the remote server. For example, information about the visitors' screen sizes, or the price of the goods they purchased, can be added in this way. With logfile analysis, information not normally collected by the web server can only be recorded by modifying the URL.
• Page tagging can report on events which do not involve a request to the web server, such as interactions within Flash movies.
• The page tagging service manages the process of assigning cookies to visitors; with logfile analysis, the server has to be configured to do this.
• Page tagging is available to companies who do not run their own web servers

Economic factors

Logfile analysis is almost always performed in-house. Page tagging can be performed in-house, but it is more often provided as a third-party service. The economic difference between these two models can also be a consideration for a company deciding which to purchase.

• Logfile analysis typically involves a one-off software purchase; however, some vendors are introducing maximum annual page views with additional costs to process additional information.
• Page tagging most often involves a monthly fee, although some vendors offer installable page tagging solutions with no additional page view costs.

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Tags: Web Analytics Basics, Logfile, Web Analytics technologies, Page Tagging, Web Beacon, Web Analytics