: What causes an empty referrer field in a webserver log file? Given a log line from Apache such as the following: xx.xx.xx.xx - - [04/Jan/2016:10:42:27 -0800] "GET / HTTP/1.1" 200 6861 "-" "Mozilla/5.0

@Heady270

That means that the visitor did not send a referrer for the request. That can happen if:


The user was a "direct" visitor and typed the URL into the browser bar or used a bookmark.
The user followed a link from outside the browser (for example from an email or mobile app.)
The user came to your non-secure http site from a secure https site and the browser hid the referrer for security reasons.
The user modified their browser not to send a referrer (such as using a browser extension to hide the information.)
The user is using a proxy server that removes referrer headers.
The clicked link has an HTML5 rel=noreferrer attribute.
A site uses JavaScript to link to your site. Many browsers don't send a referrer when JavaScript uses window.open or location.href to open or set a URL.
A page redirects to yours with a meta refresh. Browsers either reset or remove the original referrer with this type of redirect.
The request was made by a robot that is not programmed to send referrer information. (Even legitimate robots such as Googlebot often do not send a referrer.)


Google Analytics counts all non-referrer visitors as "direct", as long as they execute the GA JavaScript and don't have an obvious robot user agent. A significant number these "direct" visitors don't send a referrer for some reason other than typing in the URL. We know this because Groupon accidentally dropped out of search engines for a few hours. During this time period they also saw most of their so called "direct" visitors disappear. They could only conclude that most "direct" visitors in Google Analytics were actually search engine referrals.

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