Logfile analysis vs page tagging

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 some 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.^[6]

Advantages of logfile analysis

The main advantages of log file analysis over page tagging are as follows:

• The web server normally already produces log files, so the raw data is already available. No changes to the website are required.
• 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.
• Logfiles contain information on visits from search engine spiders, which generally do not execute JavaScript on a page and are therefore not recorded by page tagging. Although these should not be reported as part of the human activity, it is useful information for search engine optimization.
• Logfiles require no additional DNS lookups or TCP slow starts. Thus there are no external server calls which can slow page load speeds, or result in uncounted page views.
• The web server reliably records every transaction it makes, e.g. serving PDF documents and content generated by scripts, and does not rely on the visitors' browsers cooperating.

Advantages of page tagging[edit]

The main advantages of page tagging over log file analysis are as follows:

• Counting is activated by opening the page (given that the web client runs the tag scripts), not requesting it from the server. If a page is cached, it will not be counted by server-based log analysis. Cached pages can account for up to one-third of all page views. Not counting cached pages seriously skews many site metrics. It is for this reason server-based log analysis is not considered suitable for analysis of human activity on websites.^{[by whom?]}
• Data is gathered via a component ("tag") in the page, usually written in JavaScript, though Java can be used, and increasingly Flash is used. Ajax can also be used in conjunction with a server-side scripting language (such as PHP) to manipulate and (usually) store it in a database, basically enabling complete control over how the data is represented.^{[dubious – discuss]}
• The script may have access to additional information on the web client or on the user, not sent in the query, such as visitors' screen sizes and the price of the goods they purchased.
• Page tagging can report on events which do not involve a request to the web server, such as interactions within Flash movies, partial form completion, mouse events such as onClick, onMouseOver, onFocus, onBlur etc.
• The page tagging service manages the process of assigning cookies to visitors; with log file analysis, the server has to be configured to do this.
• Page tagging is available to companies who do not have access to their own web servers.
• Lately page tagging has become a standard in web analytics.