The visitor statistics provided by most Internet Service Providers (ISP's) are simple 'Log Analysers' that run on their servers periodically. The software is cheap (often bundled free with other software), the reports are pretty standard and the software is updated quite infrequently. Hence, server statistics are often provided free of charge to web site owners.
Server-side (Log Analyzers) and client-side (Real-Time) statistics reports track site activity in very different ways. As a result, they collect different information and may not always match. For example, real-time stats are much better at tracking unique visitors and give a much more accurate page view count.
By understanding the differences you will be in a better position to interpret the results and make more effective decisions about your business.
Log File Analyser
Your internet servers create a record of the traffic and information requests in log files. These log files include information on errors, processing time, bandwidth used, visitor IP address, where visitors came from (referred) along with additional information such as operating system or browser used.
Log file analysers typically install on a server and read your log files on a periodic basis. They interpret the data and provide a snapshot report in a readable format of the information contained in your log file.
Real Time Statistics
Another method of analyzing your web site activity is to update an optimized reporting database each time a visitor comes to your site. This method requires you (or your web developer / marketer) to place a small JavaScript on every web page that is to be tracked. This code is invisible to your site visitors. As visitors surf your site the code places a standard cookie on their computer so they are tracked as unique visitors.
Within seconds of placing this code on your site information about your visitors is securely written out to a database and is instantly available for reporting. The database is optimized for reporting web visitors and search engine statistics. Because the data is real-time you do not have to wait for a snapshot report.
Also, with the client-side real-time statistics, the software that controls the presentation of reports is run on an independant server and usually point at an independent web based service (independent from any hosting ISP). This service is 100% dedicated to visitor analysis. The software is kept constantly up-to-date - including the latest search engine tracking software. It is also tailored with the end-user or busy non-technical executive in mind. It generally has better support for graphical presentation, trend analysis, period specifications and user-defined (ie. customised) presentation.
Why Log File Analysers and Real Time Statistics May Produce Different Results
| Issue | Log Analyzer | Real-Time Statistics |
| Counting Method | Counts Hits from the Web Server Log Log unique by IP address only | Counts Visitor (Unique by Cookie and IP address) and page views |
| Reporting Method | Periodic processing and extraction from log file | Available Real-Time from any browser |
| Crawlers/Spiders | Tracked via hits | May not be counted if HTML is not viewed |
| Proxy Server Page Caching | Cached pages not counted | All Pages counted |
| Non HTML files | Non HTML files such as Graphics and downloads may be counted as page views. | Unless specifically tracked will not be double counted |
| Error Pages | Tracked in separate tables of Log File | Only counted if Java Script is able to execute |
| Redirects | Requires special configuration to track | Automatically tracks the first page viewed |