Attribution
Not provided
Also called (not provided).
Not provided is the historical keyword bucket that search engines used when they stopped sending the query to sites. It marks a visit from search where the term is hidden.
How it is measured
Since encryption of search began, most organic search visits arrive with no keyword. Analytics tools show the label in place of the term. Today the main source of keyword data is the search console, which reports queries separately.
To get terms, use the search console, which reports by page and query, but with sampling and a delay. It cannot be joined to session-level data in analytics.
Worked example
A woodworking-plans site opens an old keyword report from 2013 and finds 96 percent of organic visits under the label. The current report shows the same, 9,800 out of 10,200 organic sessions.
To learn what people ask, the owner uses the console's query report by page. The page 'build a workbench' has 31,000 impressions and a 2.8 percent click rate, which suggests a title rewrite worth testing.
How it differs
Not provided is the hidden-keyword bucket. Organic search is the channel it belongs to. The bucket is inside the channel; it does not reduce the channel's size.
Common errors
Trying to recover the keywords from analytics. Reporting the bucket as a problem with your tracking. Matching the console and analytics at session level. Ignoring the console's delay. Using old keyword data as current.
In practice
Stop looking for keywords in analytics. Use the search console by page and query, and use landing pages as the link to behavior.