What does “Other” mean for Traffic Source on Google Analytics?

Question

I logged into Google Analytics today and under 'Traffic Sources' saw: "Referring sites", "Direct Traffic", "Search Engines" and "Other". I've never seen 'other' before, and it was small (only 0.5%), but what does "Other" mean?

Answer 1

'Other' means traffic sent from:

• Email clients, via email campaigns or people sharing links to your site by email.
• Tagged links for any marketing campaigns you run.

Answer 2

'Other', in this case, is defined by exclusion.

• Referring Sites is defined by traffic where GA could detect document.referrer, and thus set the medium as referral, except if deemed as search engine traffic or overridden with manual campaign tagging.
• Search Engines is defined by referral traffic that ga.js has explicitly determined to be search traffic, as well as tagged traffic where utm_medium is set to either cpc or organic.

• Direct Traffic is defined as traffic without a referrer and no campaign tagging. This could come from manual URL entry, from an HTTPS->HTTP referral, from a non-web source (like an app), etc.

• Other is any traffic that has defined sources that doesn't meet any of the above criteria.