Examples herein involve designating a first dimension of a thread visualization based on timing of a duration of a user action, the user action corresponding to a user interaction with an application; designating a second dimension of the thread visualization based on a number of threads of the application utilized for running tasks in response to the user action, the second dimension comprising a number of parallel timelines corresponding to the number of threads; determining locations for representations of the tasks within the appropriate parallel timelines of the thread visualization based on the timing of the tasks and the threads running the tasks; and rendering the thread visualization on a display.