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Manual annotation is the foundation of creating high-quality training data. CVAT provides intuitive tools and workflows for efficient annotation across images, videos, and 3D data.

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Getting Started

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Opening an Annotation Job

  1. Navigate to your task from the Tasks page
  2. Click on a job from the job list
  3. The annotation editor opens in the Standard workspace
Bookmark annotation jobs for quick access. The URL contains your job ID and persists your progress.

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Basic Workflow

The typical annotation workflow:
  1. Select a label from the objects sidebar or drawing tool menu
  2. Choose an annotation tool (rectangle, polygon, etc.)
  3. Draw or place the annotation on the canvas
  4. Set attributes if defined for the label
  5. Navigate to next frame and repeat
  6. Save regularly with Ctrl+S

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Creating Annotations

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Drawing Shapes

Each shape type has a specific drawing interaction:

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Rectangle (Bounding Box)

Method 1: Classic (2 Points)
  1. Click the Rectangle tool or press Shift+B
  2. Select a label
  3. Click Shape to create a single-frame annotation
  4. Click and drag to draw the bounding box
  5. Release to finish
Method 2: Extreme Points (4 Points)
  1. In the rectangle tool popover, select “By 4 Points”
  2. Click the four extreme points of the object:
    • Topmost point
    • Bottommost point
    • Leftmost point
    • Rightmost point
  3. CVAT automatically fits a bounding box
Shift+B  - Activate rectangle tool
N        - Repeat last drawing action
Esc      - Cancel drawing
R        - Resize mode (after creating)

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Polygon

  1. Activate the Polygon tool (Shift+P)
  2. Select a label and click Shape or Track
  3. Click to place each vertex of the polygon
  4. Double-click the first point or press N to close the polygon
Best Practice: Place vertices at corners and along edges where the object boundary changes direction. You can always add or remove points later.

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Polyline

  1. Activate the Polyline tool (Shift+L)
  2. Click to place vertices along the line
  3. Press N or double-click the last point to finish
Use polylines for:
  • Lane markings
  • Boundaries
  • Trajectories
  • Linear features

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Points

  1. Activate the Points tool (Shift+.)
  2. Specify the number of points (optional)
  3. Click to place each point
  4. Press N after placing the last point, or let CVAT auto-finish after reaching the specified count
Points are useful for:
  • Small objects
  • Center points
  • Multiple instance counting
  • Sparse annotation

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Ellipse

  1. Activate the Ellipse tool
  2. Click and drag to define the ellipse center and initial radius
  3. Move the mouse to adjust the shape
  4. Click to finish

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Cuboid

Method 1: From Rectangle
  1. Draw the front face as a rectangle
  2. Adjust the 3D depth by dragging the rear face
Method 2: By 4 Points
  1. Select “By 4 Points” method
  2. Click four corners of the cuboid’s visible faces
  3. CVAT constructs the 3D cuboid
Use cuboids for:
  • Vehicles
  • Buildings
  • Furniture
  • Any object with clear 3D structure

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Shape vs. Track Mode

When creating an annotation, choose between: Shape Mode
  • Single-frame annotation
  • Object appears only on current frame
  • Use for static images or one-time appearances
Track Mode
  • Multi-frame annotation with interpolation
  • Object persists across frames
  • Use for videos and image sequences
  • CVAT automatically interpolates position between keyframes
You can convert shapes to tracks (and vice versa) after creation using the context menu.

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Editing Annotations

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Selecting Objects

  • Click any shape on the canvas to select it
  • Tab: Cycle through overlapping objects
  • Shift+Click: Select multiple objects
  • Click an object in the sidebar to select it

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Moving Objects

  1. Select the object
  2. Drag it to a new position
  3. Or use arrow keys for pixel-perfect movement:
    • Arrow keys: Move 1 pixel
    • Shift+Arrow keys: Move 10 pixels

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Resizing Objects

  1. Select the object
  2. Drag the control points (corners, edges, or vertices)
  3. Hold Shift while dragging to maintain aspect ratio
Press R after selecting an object to enter resize mode, then use arrow keys for precise adjustments.

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Editing Polygon/Polyline Points

  1. Select the polygon or polyline
  2. The vertices become visible as control points
  3. Drag vertices to reposition them
  4. Add vertex: Click on an edge where you want to insert a point
  5. Remove vertex: Select it and press Del, or right-click and choose “Delete point”

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Editing Masks

For mask annotations, use the brush toolbox: Brush Tools (available when editing masks):
  • Brush (Shift+1): Paint to add mask area
  • Eraser (Shift+2): Erase mask area
  • Polygon Add (Shift+3): Add polygonal regions to mask
  • Polygon Remove (Shift+4): Remove polygonal regions from mask
Brush Settings:
  • Adjust brush size (1-100 pixels)
  • Choose brush form (circle or square)
  • Control opacity
Shift+1  - Brush tool
Shift+2  - Eraser tool
Shift+3  - Polygon add tool
Shift+4  - Polygon remove tool
[        - Decrease brush size
]        - Increase brush size

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Annotation Properties

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Attributes

If your labels have defined attributes:
  1. Select an object
  2. Expand the DETAILS section in the objects sidebar
  3. Set attribute values:
    • Checkboxes: Toggle on/off
    • Radio buttons: Select one option
    • Dropdowns: Choose from list
    • Text fields: Enter custom text
    • Numbers: Enter numeric values
Attributes can be set as “mutable” (can change per frame in tracks) or “immutable” (same value across all frames).

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Object States

Control object visibility and behavior with state toggles:
StateShortcutDescription
LockLPrevent editing (object becomes unselectable)
HideHHide from canvas (still saved)
OutsideQMark object as outside frame boundary (in tracks)
OccludedOMark object as occluded/obscured
KeyframeKMark current frame as a keyframe (in tracks)
PinnedPFix object position (prevents automatic interpolation updates)
L          - Toggle lock
H          - Toggle hidden
T+L        - Lock all objects
T+H        - Hide all objects
Q          - Toggle outside
O          - Toggle occluded
K          - Toggle keyframe
P          - Toggle pinned

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Label Assignment

Change an object’s label:
  1. Select the object
  2. Click the label name in the objects sidebar
  3. Choose a new label from the dropdown
Quick label shortcuts:
  • Ctrl+1 through Ctrl+9: Assign labels 1-9
  • Configure in task label setup

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Color and Appearance

Customize object colors: Global Settings:
  • Color by Label (default)
  • Color by Instance (unique color per object)
  • Color by Group (same color for grouped objects)
Per-Object Color:
  1. Right-click the object
  2. Select “Change color”
  3. Pick a custom color

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Keyboard Shortcuts

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Essential Shortcuts

Ctrl+S       - Save annotations
Ctrl+Z       - Undo
Ctrl+Shift+Z - Redo
Esc          - Cancel current action / Select cursor tool
F1           - Fit image to viewport
F2           - Settings
F3           - Keyboard shortcuts reference

N            - Repeat last drawing action
Shift+N      - Redraw selected shape
Shift+B      - Rectangle tool
Shift+P      - Polygon tool
Shift+L      - Polyline tool
Shift+.      - Points tool
Esc          - Cancel drawing
Enter        - Finish polygon/polyline

Del          - Delete selected object
Ctrl+C       - Copy selected object
Ctrl+V       - Paste object
Ctrl+X       - Cut object
Ctrl+B       - Propagate object to next frames
Tab          - Switch between overlapping objects
+/-          - Increase/decrease object Z-order
Ctrl++/-     - Increase/decrease multiple selected Z-order

L            - Toggle lock
H            - Toggle hide
Q            - Toggle outside
O            - Toggle occluded
K            - Toggle keyframe
P            - Toggle pinned
T+L          - Lock all
T+H          - Hide all

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Best Practices

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Accuracy Tips

Precise Boundaries

Zoom in (Ctrl+Wheel) when drawing to ensure pixel-accurate boundaries, especially for small objects

Consistent Labeling

Follow project annotation guidelines for consistency. Establish clear rules for edge cases

Occlusion Handling

Mark partially visible objects as occluded. Annotate visible portions only

Regular Saves

Save frequently (Ctrl+S) to avoid data loss. CVAT auto-saves at configurable intervals

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Efficiency Tips

  1. Use keyboard shortcuts - Learn at least 5-10 most common shortcuts to double your speed
  2. Shape vs Track - Use tracks for videos to leverage interpolation
  3. Copy and adjust - Copy similar objects (Ctrl+C, Ctrl+V) and adjust instead of drawing from scratch
  4. Lock completed objects - Prevent accidental edits by locking finished annotations
  5. Filter objects - Hide objects you’re not currently working on
  6. Repeat drawing - Press N to quickly redraw with the same label and settings
The N key is your best friend! It repeats your last drawing action with the same settings, perfect for annotating many similar objects quickly.

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Quality Checks

Before marking a job as complete:
  • All objects are labeled
  • Boundaries are accurate
  • Attributes are set correctly
  • Occluded objects are marked
  • No duplicate annotations
  • Objects outside frame are marked with “Outside” flag
  • Track consistency (objects maintain same ID across frames)

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Common Issues

The object may be locked. Press T+L to unlock all objects, or find the object in the sidebar and click the lock icon.
Ensure you’ve selected a label first. Some tools are only available for certain label types (e.g., skeleton tool requires a skeleton label).
Check your network connection. Use Ctrl+S to manually save. Check the browser console for errors.
You need at least 3 points. Double-click the first point or press N to close the polygon.
For tracks, make sure “Outside” is not checked on that frame. For shapes, remember they only exist on one frame.

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Next Steps

Shapes and Objects

Learn about all annotation types in detail

Auto-Annotation

Speed up annotation with AI models

Advanced Tools

Master interpolation, tracks, and propagation

Editor Overview

Explore the complete editor interface

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