NoldusViso – Annotate sessions using events, tasks and subjects
Last updated: Nov 09, 2026
Annotating a session lets you mark events and tasks directly on the video as they happen, and connect them to the subjects they belong to. That turns a raw recording into something you can actually work with:
- Debrief a session quickly, without rewatching it from start to finish
- Jump straight to the interesting parts, task by task or event by event
- Share an annotated recording so viewers and reviewers can navigate it just as quickly
- Let other annotators add their own markers, during the recording or afterward
This is useful across research, UX work, training, and debriefing alike — anywhere the point isn't just to have the video, but to be able to find what matters in it.
Prerequisites
- A recorded (or currently recording) session is needed to annotate — see Record a Session.
- Defining subjects, tasks, and events in a scenario requires an Administrator or Researcher/Trainer role — see User Accounts and Roles.
- Students/Trainees can annotate sessions that have been shared with them, within the permissions granted by the owner — see User Accounts and Roles and Session sharing.
1. Defining subjects, tasks, and events in a scenario
Subjects, tasks, and events are defined when creating or editing a scenario. Open the Scenarios tab and create a new scenario, or open an existing one to edit it.

- Subjects — the people appearing in the recording.
- Tasks — things that happen over a duration (e.g. writing, walking).
- Events — things that happen at a single point in time (e.g. an error, a hit).
Add each of these to the scenario via Add subjects (optional), Add events (optional), and Add task lists (optional).

While setting these up:
- You can assign a keyboard shortcut to each subject, task, and event, so you can annotate quickly without reaching for the mouse.

- Give each event and task a distinct color — this keeps the timeline readable once several subjects, tasks, and events are running at the same time.


- Think through whether your tasks are mutually exclusive (e.g. sitting vs. walking — only one can be active at a time) or can run in parallel (e.g. a UX test on screen and talking out loud at the same time). Tasks within the same task list are mutually exclusive; tasks in different task lists can run in parallel.

- Keep the scheme simple. An overcomplicated set of subjects, tasks, and events is harder to annotate consistently and harder to debrief afterward.
- Test your scheme with a short trial recording before inviting real participants.
- You don't need to get it perfect up front — annotations can always be added or edited later, live or in replay.
Once everything is set up, give the scenario a clear name and save it.

Free-form comments can also be added to the timeline, for anything that doesn't fit a predefined task or event.
2. Annotating live during recording
- Click New session on Home or Observe and choose the scenario you want to record — see Record a Session.

- Start the recording with the red record button below the video.

- If the scenario has multiple subjects, select the subject you want to annotate. Events and tasks can be added per subject, or to a general line that isn't tied to any specific subject.
- Click an event button (or use its keyboard shortcut) to place a marker on the timeline at that exact moment, for the selected subject or the general line.
- Click a task button to start tracking that task's state for the selected subject or the general line; click it again (or a different task in the same mutually-exclusive group) to end it.

- Add free-form comments to the timeline as needed.
- Stop the recording when done and name the session in the dialog that appears. The session, with all its annotations, is saved and available in the library.


The timeline below the video feeds, and the annotation log, both update in real time as annotations are added — so everyone watching (that has permissions to see annotations, e.g. invited Reviewers and Annotators) can follow along as they happen.
Note: You can invite others to view, review, or annotate alongside you while the recording is happening — see Share sessions.
3. Editing and reviewing annotations afterward
Annotations aren't locked in once recording stops. You can add, edit, or delete events, tasks, and comments afterward — pausing the replay, adjusting a task's duration, zooming in on the timeline, and using the annotation log to jump straight to what you need. This full workflow is covered in Review and Present Sessions.