Merge Polygons in Shapefile

Merge polygons from a shapefile online

The MK Tech Tools Merge Polygons tool is a browser-based GIS utility for combining selected polygon features from a single shapefile. It is useful when a GIS layer contains boundaries that need to be joined into a larger area without opening a full desktop GIS application.

You can upload a ZIP containing the standard shapefile components, view the polygons on an interactive map, click the features you want to combine, and merge the selected geometry. The rest of the features remain in the layer, so the result is an edited version of the same dataset rather than a completely separate geometry.

When is polygon merging useful?

Polygon merging is common in administrative mapping, survey planning, health and demographic analysis, land management, environmental work and many other GIS workflows. A few common examples include:

How to merge polygons in a shapefile

1. 1. Prepare the ZIP. Keep the .shp, .shx, .dbf and, where available, .prj files together in one ZIP archive.
2. 2. Upload the layer. The tool reads the shapefile and displays its polygon features on an interactive map.
3. 3. Select polygons on the map. Click each polygon that should be part of the merged feature. Selected polygons are visually highlighted.
4. 4. Merge the selection. Once two or more features are selected, click Merge Selected Polygons. The selected geometries are combined and replaced by the merged result.
5. 5. Review and download. Inspect the edited map and download the resulting layer as GeoJSON.

Merge versus dissolve: what is the difference?

In GIS, merge can mean several different things. This tool merges selected features within one polygon layer. It does not append two separate shapefiles together. Combining two separate shapefile datasets is handled by the dedicated Combine Shapefiles tool.

A dissolve operation usually combines features automatically according to a common attribute value, such as province name or zone code. Here, the user explicitly chooses which polygons to combine. This makes the tool useful for quick, controlled edits where only particular features should be joined.

What happens to the attribute data?

A polygon can have many attribute fields, and selected polygons may contain different values. The current version uses a simple and predictable rule: the newly merged feature inherits the attributes of the first selected polygon.

This avoids silently summing, averaging or concatenating fields that may have completely different meanings. If the values need to be changed, the resulting GeoJSON can be edited in another GIS application or in a future attribute-editing feature on MK Tech Tools.

Can non-adjacent polygons be merged?

Yes. The selected polygons do not necessarily need to share a boundary. When separate polygon parts are combined, the result may be represented as a MultiPolygon. This is valid GeoJSON geometry and is commonly used in GIS datasets for areas consisting of multiple disconnected parts.

Private, browser-based GIS processing

The tool is designed to process the uploaded GIS data in the browser. This approach keeps the workflow fast and reduces the need to send the entire shapefile to a separate GIS processing service. It is particularly useful for routine boundary edits, testing and lightweight GIS tasks.

Because processing happens on the user's device, extremely large or highly detailed layers can require substantial browser memory. For very large datasets, a desktop GIS package may still be more appropriate.

Supported input

Frequently asked questions