Appearance
Understanding the Timeline
The timeline is the heart of StarZero Agents's visual editor. It's where your video project lives -- showing all your clips laid out in order, exactly as they'll appear in your final video.
Opening the Editor
You can open the timeline editor from the sidebar, or StarZero Agents may suggest opening it when you're ready to fine-tune your project. The editor opens alongside the chat, so you can continue talking to StarZero Agents while working visually.
What You'll See
The editor has several key areas:
The Preview Player
At the top of the editor, you'll find the preview player. This plays back your project as it will look in the final render. Use it to check how clips flow together, verify timing, and make sure everything looks right.
The Video Track
The main area of the timeline shows your clips laid out left to right, in the order they'll play. Each clip appears as a block with:
- A thumbnail preview so you can see what's in the clip at a glance
- A duration indicator showing how long the clip is
- Shot boundary lines — subtle dotted vertical lines marking where camera cuts and transitions occur in the source footage. These appear automatically once the video has been analyzed and help you see the internal structure of a clip at a glance, making it easier to find natural cut points. If a clip has many rapid cuts, the lines hide to avoid clutter, and reappear when you zoom in.
In addition to regular video clips, the video track can also contain SVG clips — animated or static graphics placed directly on the timeline. SVG clips are displayed with a distinct "SVG" label so you can tell them apart from video content at a glance. They can be moved, trimmed, and animated with keyframes just like regular clips. See SVG Graphics for more on creating and using SVGs.
The Audio Track
Below the video track, you'll see a separate audio track. This is where any additional audio lives -- background music, voiceover narration, or other audio clips that play alongside your video. Audio from your video clips themselves is managed per-clip (you can adjust the volume or mute each clip individually).
The Overlay Track
Below the audio track, you'll see the overlay track. This shows any overlays in your project -- picture-in-picture video, SVG graphics, logos, and other visual elements that layer on top of your main video. Overlay clips are color-coded by type and can be dragged to reposition or trimmed using handles, just like video clips. See Overlays for details.
The Time Ruler
Along the top of the timeline, a ruler shows timestamps so you always know where you are in your project. This helps you understand the total length of your video and the position of each clip.
Timeline Controls
Play and Pause
Use the play button (or press the spacebar) to preview your project. The playhead moves across the timeline showing your current position.
Playback Speed
Click the speed button in the controls bar to cycle through playback speeds. This lets you quickly review footage at a faster pace or slow things down for precise editing. The current speed is displayed on the button (e.g., "1x", "1.5x", "2x"). This only affects preview playback — your final render always plays at normal speed.
Scrubbing
Drag the playhead along the timeline to quickly jump to any position. You can also click and drag anywhere on the time ruler to scrub -- you don't need to grab the playhead itself. This is the fastest way to navigate through your project and check specific moments. When you pause, the playhead snaps to the nearest frame so you always land on a real, renderable moment -- useful when you're trying to pick the exact frame for a keyframe or a split.
Playhead Controls
When playback is paused, a small control bar appears at the playhead showing the current timestamp and three quick-action buttons:
- Split (scissors icon) -- split the clip under the playhead into two separate clips
- Trim start ( [ ) -- remove everything before the playhead in the current clip
- Trim end ( ] ) -- remove everything after the playhead in the current clip
These controls give you fast, precise editing without needing to type commands. The split button is disabled when the playhead is too close to a clip boundary (within one frame). The controls hide automatically during playback so they don't get in the way.
Zooming
Use Ctrl + scroll (or Cmd + scroll on Mac) to zoom in and out on the timeline:
- Zoom in for fine-grained editing -- this stretches the timeline so you can see individual frames and make precise adjustments. When you zoom in far enough, the time ruler starts showing individual frame tick marks so you can see exactly where each frame begins and ends.
- Zoom out for an overview -- this compresses the timeline so you can see your entire project at once
On touch devices, you can pinch to zoom with two fingers directly on the timeline. The zoom stays centered on the midpoint between your fingers, so you can zoom into a specific section without losing your place.
The Side Panel
On the right edge of the editor, a vertical icon bar gives you quick access to editing tools:
- Transcript -- view and edit the transcript inline
- Captions -- browse and apply caption presets
- Clip -- view and edit the selected clip's framing, volume, keyframes, and more (see Clip Controls)
- Split Screen -- create and edit split-screen layouts on the clip under the playhead (see Split-Screen Layouts)
- Feedback -- add comments and annotations at specific moments (a badge shows how many markers you have)
- Project & Settings -- switch between projects and change the aspect ratio visually
Click any icon to open its panel. Click again to close it.
Project Selector
If you've saved multiple versions of your project within the same chat, you can switch between them using the Project & Settings panel in the side panel. This is useful when you're experimenting with different arrangements or trying out alternative edits.
Selecting Clips
Click any clip on the timeline — video, audio, or overlay — to select it. The selected clip stays clear and bright while the rest of the timeline dims, so it's easy to see exactly what you're working with. Only one clip is selected at a time, across all tracks.
Selecting a clip is how you reveal its editing controls:
- Trim handles appear on the left and right edges of the selected clip, so you can adjust where it starts and ends (see Trimming Clips)
- Move arrows appear just outside a selected video clip, letting you step it one position left or right (see Reordering, Splitting, and Removing Clips)
To deselect, click an empty area of the preview or press Escape. If a clip you've selected is later removed — by you or by a change StarZero Agents makes — the selection clears automatically.
Keyboard Shortcuts
Once the editor is open, you can drive most of it from the keyboard. Click the keyboard icon in the bottom-right of the preview player at any time to see the full list inside the app.
Playback
| Shortcut | Action |
|---|---|
| Space | Play / pause |
| ← / ↑ or → / ↓ | Step back / forward one frame |
| Shift + ← / ↑ or Shift + → / ↓ | Step back / forward one second |
Navigation
| Shortcut | Action |
|---|---|
| , | Jump to the previous keyframe |
| . | Jump to the next keyframe |
History
| Shortcut | Action |
|---|---|
| Ctrl + Z (Cmd + Z on Mac) | Undo |
| Ctrl + Shift + Z or Ctrl + Y | Redo |
Editing
| Shortcut | Action |
|---|---|
| K | Split the clip under the playhead into two |
| [ | Trim the clip start to the playhead position |
| ] | Trim the clip end to the playhead position |
Selected keyframe
| Shortcut | Action |
|---|---|
| Ctrl + C (Cmd + C on Mac) | Copy the selected keyframe |
| Ctrl + V (Cmd + V on Mac) | Paste onto the selected keyframe |
A copied keyframe stays available across projects and browser tabs, and pastes onto another keyframe of the same kind (framing, volume, or overlay) — volume keyframes carry between audio clips and video clips. Copying a keyframe replaces whatever was on your clipboard, and the copy pastes nothing outside StarZero Agents.
Frame-stepping is especially handy for finding the exact moment to split a clip or place a keyframe -- zoom in far enough to see frame ticks, then nudge the playhead one frame at a time.
Working with the Timeline
The timeline editor and the chat work together. Changes you make in the editor are reflected in the chat (StarZero Agents will acknowledge what you've done), and changes you request through conversation appear in the editor immediately. You can freely switch between the two approaches at any time.