There could be a various number of reasons why Piwik numbers are different from your other web analytics solution.

  • Identifying Visitors: Piwik uses a javascript based tracker, and keeps count of unique visitors using a first party uuid cookie, as well as a visitor recognition heuristics algorithm (based on IP address and user settings). Some other tools only use cookies, only use IP, or a combination: we found that the way Piwik tracks visitors gives us really good accuracy and avoids creating artificial visits.
  • Tracking method: Other softwares (such as AWStats, Webalizer, Analog, etc.) or custom server-side script would record all traffic, including search bots or spam bots. By default Piwik uses a Javascript tracker which automatically only records “real” human activity. This leads to more accurate reports. (PS: Piwik can still track search engine bots separately)
  • Hits vs Visits: Log analyzers softwares will typically report “hits”. Hits generally count all http requests to your websites: pages, images, css, javascript files, etc. Piwik reports page views, unique visitors, visits, etc. whiLogs analyzersch are expected to be much less than the number of hits.
  • Record loaded page: when the Piwik javascript code is located at the end of the page, Piwik will only record page views for page that are finished loading. Log Analyzers would also record page requests that have been “cancelled”, eg. when the user hits the Back button before the page is displayed.
  • Position and presence of Javascript tag: when comparing Javascript-based statistics (eg. number of unique visitors), you have to make sure that both javascript tags are present on all pages you want to track. Also, it is better to put all tracking codes at the end of your pages, just before the tag.
  • DoNotTrack support: Piwik by default respects the DoNotTrack setting. If visitors have selected not to be tracked in their browser, Piwik will not collect information about them. If you suspect many of your users are using DoNotTrack, you can disable it in the Privacy settings.

Concerning Google Analytics, several users compared Piwik and Google Analytics numbers, and found very similar statistics: on significant traffic, differences were always less than 5 percent.

Conservative counting is definitely best – it makes your statistics more realistic on what you are trying to measure. Most analytics packages are used to measure relative upswings, we recommend using the same tool for all measurements and relative comparisons.

See also the FAQ: Piwik tracks a lot less visits than other web analytics tools, but tracks the same number of pageviews.