Write SQL query to solve given problem: Which category has the highest number of users?. Keep the solution inside sql tag ```sql [SQL-Query] ```
SELECT T.category FROM ( SELECT T2.category, COUNT(T1.app_id) AS num FROM app_labels AS T1 INNER JOIN label_categories AS T2 ON T2.label_id = T1.label_id GROUP BY T1.app_id, T2.category ) AS T ORDER BY T.num DESC LIMIT 1