> For the complete documentation index, see [llms.txt](https://docs.imerit.net/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.imerit.net/labeling/labeling-tools/tools/polygon.md).
# Polygon
The polygon labeling tool allows you to draw a polygon around an object or point of interest in an image.
{% hint style="info" %}
The Polygon tool is supported across the Image, Video, and DICOM labeling editors.
{% endhint %}
{% hint style="info" %}
If you are deciding between Polygon and Segmentation, see [What's the difference between the Polygon tool and the Segmentation tool?](/other/whats-the-difference-between-the-polygon-tool-and-the-segmentation-tool.md)
{% endhint %}
## How to add a Polygon tool to your project
From the project’s *Settings* tab, enter the *Label Set* section.
Click on *Add Category*. From the list that appears, click on *Polygon*.
A new row will appear named *Polygon*. Click on it to expand it.
Give your polygon tool a title and description.
Enable the **Required** toggle if you want to force labelers to create a polygon on every asset. When the toggle is disabled, labelers will be able to save and move to the next asset without creating a polygon.
If you would like for your polygon to appear curved, enable the **Curved** toggle. Please note that this is a purely visual change and does not affect the final export in any way.
If you would like to ask labelers further questions, for example, if you want to show a further *radio* after drawing the polygon, click on *Add Classification* and add a further question. More[ on nested questions here](/labeling/labeling-tools/tools/nested-classifications.md).
## How to Draw a Polygon
Click on the image where you’d like the first point of the polygon to be. Click again where you’d like the second point to be, and so on. When you are done, click on the first point again or press on *N* on your keyboard to close the polygon.
While drawing, you may click anywhere with the right mouse button to delete the last point you have placed.
To add a new point after closing the polygon, hold CTRL and click anywhere on an edge to add a point. To delete a point, hold CTRL and right-click on the point you’d like to delete:
To quickly trace a polygon without having to click on each point manually, after having drawn the first point, hold *Shift* then start moving your cursor:
## Editing Polygons
After selecting a polygon in the labeling editor, you can use the polygon editing controls to modify it:
* **Auto-Overwrite**: Draw a new polygon that removes overlapping areas from existing polygons.
* **Auto-Subtract**: Draw a new polygon that excludes areas already covered by existing polygons.
* **Auto-Merge**: Select a polygon, then draw an additional area to merge into that polygon.
* **Eraser**: Select a polygon, then draw an area to remove from it.
* **Merge**: Select multiple polygons and click *Merge* to combine them.
* **Subtract**: Select two polygons and click *Subtract* to remove the first selected polygon's area from the second selected polygon.
While drawing with **Auto-Merge** or **Eraser**, the selected polygon stays fixed so the new outline can be completed without accidentally dragging the existing annotation. Press *Esc* to cancel an unfinished helper-tool outline before applying it.
Polygon annotations can contain only one region and no holes. If an editing operation would create multiple separate regions or create a hole, Ango Hub will not apply the operation and will show a warning.
## Edge Sharing
While drawing a polygon, if you press E, Hub will highlight the points of other polygons, polylines, and points. By clicking on the other object's points, you can snap your current polygon's points to them:
You can also share edges with the polygon itself the same way:
By snapping at least two points to the existing polygon and holding Alt (⌥ on macOS) + clicking, you can quickly anchor a series of points to the existing object:
## Nudge Tool
You can apply small changes to your polygons by 'nudging' them.
To nudge a polygon, click on the polygon on the asset, then pick the type of nudge tool you'd like to use:
Nudge Erase will allow you to reduce the size of your polygon while applying small changes. Nudge Draw will add area to your polygon.
Once you have picked your nudging tool of choice by clicking on either the "plus" or the "minus", click and drag around the polygon's edge to refine the edge of your polygon:
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