Attribution
Unassigned traffic
Also called other channel.
Unassigned traffic is sessions that match no channel rule in the grouping table. It marks a gap in your rules or tags.
How it is measured
When a session's source and medium fit none of the rules, the tool puts it in a catch-all bucket. A large share signals missing rules, odd mediums, or tags with unexpected values.
Open the bucket and list the source and medium pairs inside. Rank them by sessions. The top few usually explain most of the problem.
Worked example
A craft-fair marketplace sees 1,860 unassigned sessions out of 14,500. The top pair is 'partner-feed / feed' with 1,120 sessions, from a product feed to a comparison site.
The marketplace adds a rule mapping medium 'feed' to a Shopping channel. The unassigned share drops from 12.8 percent to 3 percent. Next, the owner finds one email vendor using medium 'mail', which also needs a rule.
How it differs
Unassigned traffic matches no rule. Direct traffic has no source at all. A visit can have a source and still be unassigned if the grouping does not know it.
Common errors
Ignoring the bucket. Adding rules without testing. Using many odd mediums. Expecting zero. Forgetting to rerun history after fixing rules.
In practice
Look at the bucket each month and add a rule for the top unmatched pair. Standardize mediums so new campaigns fall into a rule on their first day.