1. Learn the four parts of the editor

EditPolygon is arranged around a map, with project controls on the left and feature-specific controls on the right. The top toolbar handles files, undo, search and export. The left tool rail switches between selection, drawing, vertex editing, images, measurement and annotations.

Top toolbar

Open, save, undo, fit, search, choose export scope and export format.

Project and Layers

Import files, control visibility, select multiple features, create groups and reorder layers.

Map

Select geometry, draw shapes, see previews and use context-sensitive toolbars.

Inspector

Rename, inspect metrics, edit geometry, change style, manage holes and export the active feature.

2. Import a polygon file

Choose Open.
Select one or more GML, KML, KMZ, GeoJSON, JSON, CSV, WKT/TXT or zipped Shapefile files. You can also drag files onto the Project import area.
Review the import preview.
For complex files, check the detected file name, feature count and geometry type before importing. Very large files may offer optimised, sleeping or reference-overlay modes.
Confirm the layer.
The file appears under Layers. Use the arrow to expand it. The eye controls visibility; the checkbox controls selection.

Browser-local processing. Imported geometry is read in your browser. Keep the original source file because any editing or conversion workflow can change precision, attributes or structure.

3. Select and inspect a feature

Click a polygon on the map to make it active. You can also click its row in Layers. The Inspector updates immediately with its name, geometry type, vertex count, area, perimeter, bounds and available tools.

A polygon selected on the map with the corresponding layer row and Inspector panel active — The active feature is highlighted on the map and in Layers. The Inspector is the safest place to confirm you selected the intended polygon.

Multiple selection

Ctrl-click on Windows or Linux, or Command-click on macOS, toggles an additional polygon.
Shift-click selects a range in the current Layers order.
The layer checkbox selects or clears every feature in that layer.
Eye and lock controls do not change selection.

4. Edit the polygon

Select Edit vertices to move individual coordinates. Red handles are existing vertices. Green midpoint handles insert a new vertex when clicked. Snapping helps match nearby boundaries, while topology mode can move matching shared vertices in other visible polygons.

Polygon in vertex editing mode with red vertex handles, green midpoint handles and the vertex toolbar — Drag red handles to reshape the polygon. Use midpoint, snapping and topology controls deliberately—especially when neighbouring polygons share boundaries.

Before deleting vertices: zoom in, confirm the correct vertices are selected, and keep enough coordinates to form a valid closed ring. Use Undo immediately if the shape changes unexpectedly.

Other editing methods

Geometry code: inspect or replace the selected geometry as GeoJSON coordinates.
Geometry tools: merge, cut, intersect, clip, erase, split, repair, simplify, smooth, offset or manage holes.
Inspector values: true GML circles expose centre and radius controls instead of polygon vertices.

5. Organise layers and drawn features

Create additional drawing groups with + New group. The active draw target receives newly drawn polygons. Drag polygons within a layer to reorder them, or drag them onto another layer header to move them between groups. Drag layer headers to change layer order.

Use sorting when manual order is not useful: name, north-to-south, east-to-west, area, vertex count or original import order. Clear searches and filters before manual reordering.

6. Validate before export

Open More → Validate / repair polygons. Use the current project or load a separate file, review each issue, and start with Recommended fixes rather than applying everything automatically.

Validate and repair modal showing two geometry issues and recommended fixes — Validation is a review step, not a guarantee that the geometry is operationally correct. Inspect the repaired shape on the map.

7. Export the correct scope and format

The top-right controls choose All, Selected or Visible geometry. KML is the initial format when the app opens. The Export window lets you change format, filename and coordinate precision.

Export window showing scope, KMZ format, filename, precision and a true-circle conversion notice — Verify the export summary before downloading. When a true GML circle is exported to a non-GML format, only the downloaded copy is approximated with vertices.

8. Save and recover work

Save creates an EditPolygon project file containing layers, features and editor state.
Autosave stores recovery data in the current browser. It is not a replacement for downloading a project file.
Restore autosave is available under More.
Exported GIS files contain geometry for another system; project files preserve more editor-specific state.

Troubleshooting

A file imports but nothing is visible

Use Fit, expand the layer and confirm both the layer eye and feature eye are enabled. The file may contain unsupported or non-polygon geometry, or coordinates may use an unexpected CRS.

The app is slow with a complex layer

Keep large layers collapsed, hide unneeded layers, use optimised editable import where appropriate and avoid opening full geometry code unless required.

I cannot run a geometry tool

Check that the correct active polygon is selected and that any additional required polygons are selected. Locked features must be unlocked before editing.

The exported result looks different elsewhere

Check CRS assumptions, coordinate precision, holes, styling and format-specific limitations in the receiving application.

Beginner completion checklist

The intended file and layer are visible.
The correct feature is active.
Edits were reviewed at a useful zoom level.
Validation issues were reviewed rather than blindly accepted.
The correct export scope and format were selected.
The original source and an EditPolygon project file were retained.