User Interface

The main window is built around one idea: the image gets the space, the controls stay at the edges.

┌──────────────────────────────────────────────────────────────┐
│ Top bar — menu · undo/redo · image navigation · save · view  │
├────┬──────────────────────────────────────┬──────────────────┤
│ T  │                                      │ Objects / Labels │
│ o  │                                      │──────────────────│
│ o  │               Canvas                 │ Appearance       │
│ l  │                                      │──────────────────│
│ s  │                                      │ Image Settings   │
├────┴──────────────────────────────────────┴──────────────────┤
│ Status bar — tool · label · cursor · zoom · annotation count │
└──────────────────────────────────────────────────────────────┘

Top bar

From left to right:

Logo button — clicking the logo cycles the UI theme (System → Light → Dark → Cvat). The choice is saved to the configuration file.
Menu — global operations: project management, image import (Ctrl+O), export, settings.
Undo / Redo — every annotation edit is reversible (Ctrl+Z / Ctrl+Shift+Z).
Image navigation — first / previous / next / last, a progress slider and an n / total counter. The play button steps through the project’s images automatically — useful for a quick visual pass over a batch.
Save — persists the current image’s annotations (Ctrl+S).
Fullscreen toggle.

Tool bar (left)

All annotation and navigation tools, one active at a time. The active tool is highlighted; the status bar always names it. Tools are covered in detail in Annotation tools — the short version:

Group	Tools
Navigate	Select `V` · Pan `H` · Zoom `Z` · zoom in/out · fit to window `F`
Draw	Rectangle `R` · Polygon `P` · Polyline `L` · Ellipse `E` · Point `O` · Mask brush
Modify	Slice · group/merge operations
AI	Interactive segmentation `Ctrl`+`Shift`+`A`
Meta	Image-level tags

Canvas

The canvas shows the active image and all annotations, and receives all drawing and editing input. Navigation works the same regardless of the active tool:

Zoom — mouse wheel, centered on the cursor. Ctrl+wheel is deliberately ignored so touchpad users don’t zoom by accident.
Pan — drag with the middle mouse button, or hold Space and drag with the left button, or use the Pan tool H.
Rotate view — Ctrl+R rotates the viewport clockwise, Ctrl+Shift+R counterclockwise. This rotates the view only, never the stored coordinates.
A scale bar is displayed on calibrated images.

Objects panel (right)

The right panel has two tabs plus two collapsible sections.

Objects tab

Lists every annotation on the current image with its running number and label. The header shows the total count and offers sorting, list-wide lock/visibility toggles and a text filter. Each row provides per-object controls — lock, visibility and related toggles — plus a menu with further actions, and can be expanded for details. Clicking a row selects the object on the canvas.

Labels tab

The project’s label catalog: name and color per label. The active label — the one new annotations get — is also shown in the status bar and switches instantly with Ctrl+1…0.

Appearance

Rendering controls for annotations: Fill Opacity, Stroke Opacity and a Show Borders toggle. Purely visual — nothing here changes your data.

Image Settings

Non-destructive display adjustments for the current image: Brightness, Contrast, Saturation, Gamma, a Smooth image toggle and a Reset button. These only affect what you see, never the image bytes — useful for making faint phase boundaries visible while annotating.

Status bar

Always-visible context, left to right: active tool, active label, cursor position in image coordinates, zoom level, annotation count for the current image, and the content hash of the active image.

Secondary windows and panels

Image browser (F3) — thumbnail overview of every image in the project; click to switch. Esc closes it.
Settings (F2) — application settings.
Shortcut help (F1) — the complete, generated-from-source list of keyboard shortcuts. The shortcuts reference mirrors it.